My POV is that this is a false trope.
(A) I’ve never seen a startup which I expected to have no trouble raising an A Round fail to raise an A Round (albeit sometimes at sizes and valuations tougher than they originally expected).
(B) There are many many many more seed companies being funded and raising (in an initial round or successive rounds) $2–3m. Series A investors look at a company that has spent that sum and expect to see progress.
So there are lots of statements to be made about the challenges facing seed founders, but turning it into a “Series A is harder than ever” argument just doesn’t hold water for me.