This recommendation from @CDCgov, coupled with the rationale given, beggars belief.
This is thinest of absence-of-evidence arguments.
Imagine what would have to be true of young adults for re-entry testing to not be helpful.
No transmission from asymptomatic patients.
No transmission from mildly symptomatic patients.
No pre-symptomatic transmission, or >2 day turnaround on tests.
Here is the Washington Post article from which the quote above is taken: