With D-76 type developers it is ok to begin with water temperature higher than recommended if your experience says it helps. However, they tend to recommend lowest usable temperature for dissolving chemicals so that you could use the solution without waiting too long to cool down to 20C. If you wait overnight to be absolutely sure anyway, then it doesn't matter much.(posted 8106 days ago)One exception is XTOL or anything that contains ascorbate because it decomposes easily at higher temperature. However, XTOL is easy to dissolve (no metol or hydroquinone) so you shouldn't need hot water anyway.
Metol is hard to dissolve in sulfite rich solution. Presence of base helps a bit, but Ilford ID-11 has metol and hydroquinone in a separate package to make it easy to dissolve. If you see no precipitation after dissolving part A but see something after dissolving B, that's probably borax, sulfite or inorganic minerals from tap water. This stuff, I wouldn't worry much about. But if you see something after A before B, I wound work hard to get them disappear (into water, of course). One problem with Kodak's D-76 package is that you can't tell what's in the precipitation... Well, you can see if it's particle or needle like and get some idea, but it's probably not worth worrying if you can byu ID-11 or mix your own D-76 (D-76H is simpler and just as good).
I don't know why Kodak changed the instruction... I bet my $0.05 on a hypothesis that Kodak let someone with no or little darkroom experience to revise package printing :-)