Well, I agree with you that I don't feed my worm bin onions or citrus peel (tho' no doubt there is a bit of cooked onion in some of the things that go in there).

I keep my worms in an unheated, attached garage, and I feed them plenty of fish skin and bones, chicken bones, dairy and egg. I think any mice in the garage are more interested in the dog kibble that gets spilled from the bulk bag from time to time, but I notice very few mice.

Let me share my rules for aerobic composting of food scraps. I compost food outdoors all year round in plastic compost bins, without attracting hordes of rodents. I won't say I never have a rodent, but they are periodic visitors to my yard.

Safe Food Composting Rules:

1. Never put in direct contact with soil
2. Never have food as top layer
3. Layer in absorbent carbon sources
4. Compost aerobically in hot, active pile
5. Turn the whole pile when you add food waste
6. Turn frequently

Your impression is correct, the yeasts that ferment the bokashi compost make nutrients available to plants, and uninteresting to rodents.