When I have 2 villagers which have trades and try to use them to breed, they don't breed. If 1 has no trade then they breed straight away. You dont have to have traded with them for them not to breed. As long as they hold the trade they dont breed. I have a box with 9 beds and two villagers to test for this, they get about 4 stacks of carrots. I have used fabric versions of the game to tick warp the game also to try and see if time is an issue. As soon as 1 looses their trade, breeding happens.