This is my question. Foreign athletes typically enter the U.S. on a
P-1A visa for internationally recognized athletes or an O-1 visa for those with "extraordinary ability" but they're still Visas. Maybe they'll carve out holdouts for this that the news articles aren't delving into (probably because they haven't been announced).
Many Ethiopian cross-country runners were not able to participate in the recent World Cross Country Running championships in Tallahassee Florida due to rejected visas.
The USA is also supposed to host the World Track & Field Championships for under-20 in Eugene Oregon this summer.