Making animals InLove

I'm trying to make an automatic animal breeding mechanic for vanilla animals but I can't seem to make it work.

From what I've seen the breeding stats for animals are stored in NBT tags, using the tags "Age" and "InLove".

But setting the InLove NBT tag does not seem to work. I was using /data to test it, and had particles spawning on the target to make sure it was firing, but it seems to refuse to set the "InLove" tag. I have it set up to spawn particles when it tries to set "InLove", so I can see that it correctly finding nearby animals and correctly deciding they are ready to breed (age=0 and inlove <=0), but the tag is never set, even in single player (if that would matter).

 I tried putting it inside of a queueServerWork but that made no difference. 

I've been using NBT tags quite a bit with this mod otherwise and they all seem to work fine, the only issue seems to be trying to overwrite the vanilla tags. Is there some sort of trick to make this work? I'm kind of shocked it's been such a pain in the butt already.