Outside of domain specific knowledge some people have Senior traits right away; ownership, tenacity, attention to detail, empathy to risk. They will ask for help more readily but also become blocked less than other "seniors" with years of experience(by both asking for help and trying to help themselves more).

Others will have a few years of experience and a "senior" title but may never obtain those traits.

The problem is those areas are often conflated under a single "senior" title at companies. But you definitely know who's going and who's staying when the layoffs come.