animary wrote:"...the new size mechanic..."
I mean the q of the mature tree. Every type of tree will grow on any terrain but grows best on one particular terrain (its native biome). My tree farm has three different terrains; using identical tree pots, water, mulch and seeds, I can plant a tree on each terrain and get three different q mature trees. This has been consistent across many worlds.
Your experience is directly counter to my own. Trees have a good chunk of RNG in their rolls (10 point spread), but terrain itself has never had an impact. You have the "is this considered a forest biome" yes/no question though, non-forest biomes massively slow down tree growth. There are also hidden growth speed nodes that impact how fast trees grow.
The new size mechanic from last world let trees overgrow and multiply the quality of the base tree by the % of overgrowth. An achingly slow spiraling mechanic. Trees overgrowing happens on a random tick system, meaning once trees hit maturity they can start further spreading out in quality via RNG hits.
I do a lot of testing on this stuff. Take it for what you will.