Jinchuurikis would like to refute that.
Humans that had entities forged entirely of chakra sealed into them who were said to increase the volumes of stamina of their vessel. Your refutation has a few unaccounted details to itself.
As Jiraiya has said once, Naruto has two types of chakra.
Although Kurama's presence does increase Naruto's reserves, the stamina he had at his disposal was exorbitant because of his Uzumaki heritage. Consequently, the option to develop Sage Mode would still be available to him.
This would apply to all Jinchuurikis, When Jinchuurikis summon their Bijuu's chakra, it increases their capacity.
Actually, whenever a bijuu releases their chakra it's been described as an overflowing torrent coursing through the circulatory system of the jinchuuriki. Releasing the 8 gates has a similar effect albeit to achieve that effect (temporarily) the limiters on stamina and energy are released. But I digress.
The bijuu can increase a human's natural capacity. In much the same way that Uzumaki or Senju DNA would bestow larger carrying capacities to someone who may little chakra of their own.
Now, we know that Naruto's seal mixes his chakra with Kurama's naturally over time. But who's to say that's not the case for other Jinchuurikis? There's a reason why Gaara's stats in Stamina is equal to Naruto's.
Of course, there is nothing to suggest that only the jinchuuriki of Kurama is subject to this change. Any jinchuuriki would logically experience the same phenomenon because they have a bijuu of their own enlarging their metaphorical gas tanks. People under unique circumstances receiving these boosts which they couldn't normally attain by themselves.
And if Naruto's large chakra capacity is due to both types of chakra mixing together naturally, then wouldn't mixing the chakra stored in her seal with her regular chakra essentially increase her chakra capacity?
No, because it's not a different source of chakra that she's receiving neither is there a separate entity connected to her body that is causing any fluctuations to her stamina levels. It's just her own chakra which she allocated to a seal on her forehead. If the seal were to be released the chakra would be dispersed throughout her body. No changes to the internal reservoir. There's just a greater quantity of chakra flowing through her that doesn't rectify the flaw with her insufficient carrying capacity when she is making chakra.
just like the way Naruto's seal does. Bottom line here is, it's about one's chakra stored in two different vessels. I'm not focusing on the "type", mind you. I'm focusing on the fact how both NS has two tanks of chakra stored separately and how they (can) mix together.
it's not a different source of chakra that she's receiving neither is there a separate entity connected to her body that is causing any fluctuations to her stamina levels.That's the underlying flaw to this argument. Naruto's chakra has been commingling with Kurama's ever since he was an infant. There has been time for the enormity of Kurama's supplies to directly influence Naruto's personal capacity. He's able to use chakra taxing jutsu so liberally because of that influence. Without it, Naruto would still have above average reserves, but they would pale in comparison to what he has currently.
No such influence has been stated to exist with the Yin Seal and that would be arguing with baseless fabrications when looking for a connection that doesn't exist. It's like trying to use a battery that you purchased from a store to compensate for a generator at a power plant.
Also, one can increase their chakra capacity through either training or other methods. One need to look no further than Kakashi.
You're able to refine techniques and reduce their chakra expenditure which is what Kakashi has been trying to do with his Kamui ever since P2 began. He mentioned that it was imperfect when he tried to warp Deidara's head away in the Kazekage Rescue Arc. It's not that his chakra levels were somehow miraculously augmented over the course of a few weeks to a month.
Back in Part I, Kakashi was only able to use his Sharingan for a few minutes at best. Come Part II, he's able to last a whole day using it. If that's not him increasing his chakra capacity, I don't know what is.
That has to do with him lessening the strain the Sharingan had on his body which enabled him to maintain it for longer periods of time. We see numerous examples of this refinement process taking place. Sasuke and his usage of Amaterasu being a case in point. When he first developed MS it was a chakra intensive ability that caused his eye to bleed and his reserves to be drained significantly. Fast forward past several fights and testing the strength of EMS and now he's able to use Amaterasu as frequently as Naruto uses shadow clones with no bleeding of the eyes despite him bleeding (with EMS) as the black flames were created during the Kabuto fight.That's not a result of his own reserves increasing, no. It's because he managed to perfect the technique and reduce the strain it had on his own eyes to a minute discomfort (presumably).