Doesn’t help that a large portion of the Orc population were artificially aged up with Fel magic by Warlocks. Also doesn’t help that Draenai seem to love for hundreds if not thousands of years, but also time seems to have passed slower for them when they were on the dimensional ships that they used to treacle the great dark.
Kind of think how that breaks down by their home planets solar year is probably the least complicating factor.