If it were flap suppression/slow peer detection/"the dunce bucket" there wouldn't be a long tail of convergence - it'd just be nothing until all at once. This also isn't something I've only seen on my personal AS alone, it's what I've come to expect in many enterprise cutovers while previously working at a network VAR. The personal AS is however much more carefree to move around to different random providers on a whimthough of course :).
I found some data from an oldish post by benjojo https://blog.benjojo.co.uk/post/speed-of-bgp-network-propaga... which confirm various tirr 1s do propagate updates across their networks very fast (<2ish seconds) while others certainly do not. Notably, Level 3 (now Lumen) is the largest BGP presence by prefix count and was the worst tested in the list - starting to apply at ~20s after to finishing at ~50s after. This was for announce specifically, which should be the clearer case.
I found some data from an oldish post by benjojo https://blog.benjojo.co.uk/post/speed-of-bgp-network-propaga... which confirm various tirr 1s do propagate updates across their networks very fast (<2ish seconds) while others certainly do not. Notably, Level 3 (now Lumen) is the largest BGP presence by prefix count and was the worst tested in the list - starting to apply at ~20s after to finishing at ~50s after. This was for announce specifically, which should be the clearer case.