! Onions inhibiting the growth of legumes, is it a myth?

I've seen this claim all over the place that alliums inhibit the growth of legumes and kill nitrogen fixing bacteria. However, I've not been able to factually verify this claim in the slightest, is this a myth? Is there any way to verify this? At this point, I'm wanting to just disregard it, because I can find no way to verify it.

I have crimson red clover, fixation white clover (balanza), Dutch white clover and even sweet clover that I didn't plant growing in same bed as my Texas sweet onions and I see nodules on them so I would have to say that it's a myth. I also have soft neck garlic and elephant garlic in the same bed and the clover I planted and even the sweet clover that was native is growing fine along with them. I also had ryegrass growing in there that I didn't plant growing there but I pull it out as it is too tall and might hurt my garlic n onions I'm trying to grow.

Some sort of white clover was apparently present in large quantities, and the seed still very much viable, in the ~10 year old rotten haylage bales that I used for potato mulch. It spread with enthusiasm into the onion and garlic areas...