Villagers seem to not spawn properly in Village

I searched for a librarian selling a Mending book and travel through a lot of villages (41 before finding one), and noticed an issue during my long, long journey.

Villagers seem to not appear properly in village : the importance of the issue depend on biome where the village is generated (so, perhaps it depends on the types of structure ?)

Most of villages in Plains, Taiga and Ice Plains contain only two or three villagers no matter the size of the village and the amount of houses. There are almost always Nitwits, Armorers, Blacksmiths in a lot of village, more Farmers in Plains and more Fishermen in Ice biomes. In those biomes, it seems abnormaly hard to find a Cleric or a Librarian / Cartographer, even if the Village contain several Libraries and Temples. I only found one Cleric (and no Librarian) in those biome after visiting 33 Villages.

However, my 8 remaining traveled Villages concern the Desert Biome. In this last biome, I always found at least one or two clerics / librarians / cartographers, and various Villagers from all professions. Moreover, the villages were a lot more populated : at least six villagers per Village (almost one per house), some reached height or more.

Note : I found only one Savana Village before, and the problems which are related for the Plains Village also seem to occur in it (I got only two villagers), however, only one Village isn't representative in my opinion...