The long tail of routers receiving your update doesn’t matter. Once the common transit networks get it, that’s where the rest would dump the traffic to reach you anyway. The only time slow propagation to the edges matters is the first time announcing a prefix after it has been fully withdrawn.

Using the wrong route to get the packet in your general direction still gets you the packet as long as it hits an ISP along the way that got the update.

We could fully drain traffic from a transit provider in <60s with a withdrawal with all of the major providers you get at the internet exchanges. If you weren’t seeing that your upstream ISPs may have penalized you for flapping too much and put in explicit delays.