Well, I still hold my belief it's Mokuton Sage Mode, somewhat related to this big tree, which, is quite similar if you think. A tree that blooms which is similar to Hashi's blooming forest from which he puts to sleep people, sucks chakra, same with Hashi's being able to do so with the bijuus, also for the healing part, as we saw with Naruto, when he hit zetsu, is like trees came to live which could equal Hashi's SM healing properties.
Plus, trees via the forests and slugs are related given that slugs live in the forest.
So for me, I still hold my belief that it's a somewhat linked thing, however, different in some aspects and each with his SM.
The chakra that Naruto was using at the time was Kurama's Yang half. Yang Release was explained as the ability to instill life into the lifeless. Zetsu is essentially portions of the Jubi's empty husk intermixed with Hashirama's Senju DNA. It's logical to assume that the chakra would have an effect on him since he is the very essence of Yang.
The Mokuton was shown to be replicative through the insertion of Hashirama's DNA. It's obviously related to genetic material. And the Shikkotsu area is supposedly a bone forest, not a vegetative one. There's undoubtedly a connecting element between the Mokuton and the Jubi, but a connection to the slugs seems far fetched.
One other thing. Didn't you mention some time back that you post an explanation to the whole senjutsu training regiment in the SSM topic? That would be interesting to read. There might have been a detail from the sage training explanation that was overlooked by myself or the other person who were involved as dissidents.
Gamakichi > Katsuyu > Snakes
Gamakichi can use senpou arts.
Gamakichi is OP
Gamakichi King of Frogs and Master of Sage arts.
Gamabunta remains as his child's superior in nearly every form based off of showings. And no, all of the frogs were fractionalised with the confirmation that Katsuyu is a massive singular entity. Assuming Tsunade and Sakura contributed half each to the summoning jutsu, then it's probable that the Katsuyu portions summoned earlier in the manga were but 5% of the total mass. A single digit percentage which matched Gamabunta's height. Katsuyu is twenty times Gamakichi/Gamabunta in size and it's demonstrably proven itself to be capable of enduring the most arduous of conditions (mass scaled Shinra Tensei, corrosive bijuu shroud extending upwards to 8 tails, and Chibaku Tensei).
You might as well be comparing a small rat to a human.