Very old world's biomes changed after update

I entered the option to recreate the world, and the seed listed is as follows:

6052621989823785155

Never used any kind of mod, hack or tool in my world, just the game itself.

Are you absolutely certain that biome change did not occur earlier than the 1.16 snapshots?

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Yes, I'm absolutely shure. I created a ticket in 2015 about this bug in 1.8.4 but forgot to update it (that's why I created this one), but the bug is probably older than 1.8.4

MC-82427

I totally respect your work, and I know that you have not only me to help, but I paid for the original copy of this game, and I would like you to help me fix this bug.

The report remains open, however, no one else has been able to reproduce it - until then, nothing can be done, sorry.

What if I send a copy of my world for you to test? 

that could help.

Does MC-167143 describe your issue?

Yes, but in my case the biomes have changed to the same type, but with normal temperature, without snow. Before it used to snow on them, the biomes remain the same, but not in the "snow version"

The frozen river becames just river, snowy montains became just montains, snowy taiga to taiga, etc.

I still need help. In my case the biomes don't change, just changes the temperature, lost the "snow status"