If you use F3+I (to receive the selected entities NBT) on a villager that has spawned due to a jigsaw block(world generation) you will see that these villagers have a follow range of 16 blocks instead of the intended 48 that all other villagers have (From spawn eggs, breeding etc...). I believe that this lowered follow range is the issue to this behavior.
Spook Ster
If you use F3+I (to receive the selected entities NBT) on a villager that has spawned due to a jigsaw block(world generation) you will see that these villagers have a follow range of 16 blocks instead of the intended 48 that all other villagers have (From spawn eggs, breeding etc...). I believe that this lowered follow range is the issue to this behavior.