With the introduction of data driven villager trades, several expert level mason trades that previously generated in 1.21.11 were not correctly converted and now no longer generate. The missing trades are all 16 of the glazed terracotta sell trades and 6 of the stained terracotta sell trades: brown, yellow, lime, green, cyan, and purple, as they are not enumerated in the tag file. The trades themselves are all defined in data/minecraft/villager_trade/mason/4.
The expert level mason trades are specified in data/minecraft/tags/villager_trade/mason/level_4.json.
Nicely spotted. Would you please consider creating separate reports for these separate issues?