That does actually make a good point. It's all a predestination paradox and that would certainly spike the timeline hard like it was.My first thought for the spike was that either Sylvie or Loki created the TVA sometime in the future. they have time machines. they can go back to the beginning and create it. this means that if they die in Lamentis, they cannot create it the TVA and then the timeline falls apart.
That also cleans up why they waited until she is 8 and why someone like Ravonna went to get her. She was ordered by the timekeepers (a front for Sylvie) to go at that time when she had the ability to escape and not before even though her birth would be a nexus event.
Also, that is why there are so many variant lokis, because they are the time keepers?
At this point, it's either that or that if two variants somehow merge or bond or whatever it creates its own form of timeline anomaly. Think the old trope of two of the same objects coming into contact and annihilating everything. Same concept just with some more complicated steps instead of just touching.