I think it’s more to do with the specific receptor and tissue distribution of that.
ACE2 has high expression in the testicles. Just getting infected, even possibly asymptomatically, might do the deed.
Mumps wasn’t known for being a nasty disease symptom wise. (fever, pneumonia, etc). But getting it after puberty put a damper on the swimmers.
I had mumps in Kindergarten. But my boys still swam fine enough. Not so much any more. It’s more like a lazy river.
I had all of them (like we all did “back in the day). Measles, German measles, mumps, chicken pox. Mumps made me far sicker than any of the others. German measles was pretty bad with lethargy and myalgia and that itchy rash all over but Mumps made my glands hurt so bad I wanted to die and it didn’t go away day after day.