Sub-biomes were removed from world generation, however names of them still exists in /locatebiome command and adventure time advancement
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Biomes in the /locatebiome aren't removed since there data still exist even though they don't naturally generate anymore without the use of datapacks or single biomes. This was even seen in Deep Warm Oceans before they naturally generated. Also the adventuring time report is MC-236614
The advancement thing is already tracked on another issue i think, but yeah, can confirm the non-generating biomes appearing in the locatebiome command.
I think they intentionally didn't remove them for technical/legacy reasons i believe, and depending on how world conversion is handled this might be WAI (due to these biomes already being generated on old worlds).