Not uncommon.
My daughter had exactly such a last minute crises with her grad school, suddenly requiring TBC tests, vaccinations and drug testing. And for someone who is very consciously hydrating throughout the day, a quick (first-ever) drug-test appointment will lead to: “diluted” results.
There was a lot of at-home drama about consequences, thoughts of admission possibly being rescinded, fueled by somewhat “terse” administrative responses to the need to retest…
Bottom line, once it got past low-level administrative staff, the response by the program was completely “chill” - and once she finally met her cohorts, it turned out that quite a few people had gone through one or the other version of the same.