Yes I noticed this recently when I started filtering candidates by test scores. Many spend only a few minutes and become the top candidate.
I have started reporting those to Upwork, as it cheats the system and mislead the employers and creates unfair competition.
All employers please help clean the system by doing the same and report all test cheaters and give respect to those who actually score high on tests because of their hard work.
"Many spend only a few minutes and become the top candidate."
That may be because they cheat, or it may be because some of the tests are ridiculously easy. I scored in the top 10% of the English vocab test in 5 minutes, because it's a joke.
Anyway, if someone feels it's worth cheating on an Upwork test they've basically failed at life.