I tried to and answered the way I did because I think a lot of people vastly underestimate the time and effort required to get certified for a trade. “Why can’t I just add an MD to my engineering degree?” seems like a ridiculous question, but “Why can’t I add a plumber’s or electrician’s or AMT license/certificate to my degree?” is treated as “well, that’s a good question; you ought to be able to!”
(They specifically asked about a certification not just “some coursework”.)
A pretty good set of AWS welding certs can be done in 6wk of night classes.
You can't get paid money to install a toilet in some states until you've started as the jobsite bitch, worked your way up and payed years of your life into the system to get in a position to even be eligible to take the test.
The latter tends to only happen after regulatory capture.
(They specifically asked about a certification not just “some coursework”.)