It was his “true form” in Ep3 because he was no longer masking himself. He was born a human and looked like a regular guy.

And all the new canon stuff with green cloning liquid will be based on the idea that it’s what Snoke grew out of. The red cylinders we see in TROS:A are for Palpatine’s clones, which might not be the same thing. Snoke could still have been elsewhere in a green vat if future canon demands it of your headcanon and TROS:A won’t contradict it.

At least with TROS:A you could probably assume there was a single Snoke being that was created.

There’s a handful of things in TROS:A, especially V2, that merely removes obstacles from nerdy headcanon being brought to bear.