If you install using USB Install, it includes waitusb=5:UUID=xxxx. I think that is adequate for most computers. Probably over 99%.
I suspect that most of the people having problems, are those not using USB install, but setting it up manually, and not including waitusb=5.
I will be surprised if you can find a computer which needs any longer than waitusb=10.
If waitusb=10 or 20 is implemented, it needs to be done in such a way that it does not slow down those who don't need it. Which may be somewhere between difficult and impossible.