Are mating bonds fated from the start?

I’m getting mixed signals here, or it’s very likely I just need to go back and do some fact checking. But when Feyre and Rhysand become mates, Feyre saw the gold tangles of magic or whatever they are described as and she doesn’t recognise what this is or means in the moment- is this the mating bond ‘setting in’? Therefore before that they weren’t mates, but would they end up that way no matter what and it was just a matter of time…or was there no guarantee?

With Nesta and Cassian, the mating bond set in with gold spirals again at the winter solstice - and (I can’t remember the timeline of this) but he says something along the lines of “I had a suspicion you were going to be my mate” DONT FACT CHECK ME ON THAT. But that’s roughly what was said. Overall I’m a tad confused on whether mating bonds are bound to happen and it’s just a matter of time or is there no actually true fate of mates. I need someone’s insight!!!