It's no longer senior, it's only L4 (new hires are usually L3). Also I never knew the time length for the cliff, but I think it was really, really long.
It also wasn't, as far as I know, every strictly enforced. There were folks when I joined (which was when the L5 requirement still existed, but it was in its way out) who had been L4 for like a decade.
Right, while there was a "growth" expectation for L4s written into the SWE job ladder, there were no fixed timelines. Enforcement varied from org to org: at least one of my previous orgs periodically conducted talent reviews, specifically looking at cases like long-tenured L4s to decide whether to intervene.
That was before the layoffs started. One of my by then ex-reports, who was a very talented and knowledgeable but not at all career-focused long-time L4s got laid off in one of the rounds. :(
