No one says they don’t do some lifting, probably quite “heavy” in some peoples mind, but they aren’t doing a bunch of 1-3rm heavy lifts on a routine basis.
Where do they get that specific strength - 20x30-40m hills would do that I would think. At least that is what Powell has done and probably Bolt. Add sled pulls that Powell and Bolt do as well. I bet they get better specific strength from that than they ever would with weights.