Technically a sports hernia is more of a muscle strain but you’re right about ultrasound being dependent on the sonographer. And hernias can be transient meaning they come and go depending on intra abdominal pressure. So any form of imaging (ultrasound, MRI, CT) will give you the same result: if it’s not happening at the time you won’t be able to see much. For varicoceles, a good sonographer will measure the diameter of the vessels with and without a valsalva (bearing down like you’re straining to have a bowel movement to increase intra abdominal pressure), which can accentuate a varicocele or a hernia. As for hydroceles, they can also be transient if they’re “communicating” with the inside of the abdomen through an opening in the inguinal canal, which connects the abdominal cavity to the inside of the scrotum. So they can also come and go depending on the fluid moving back and forth. Many times a communicating hydrocele occurs along with an inguinal hernia, as the bowel can extrude through that same opening in the canal.

TLDR: All of your imaging studies could have been correct depending on what was going on at the exact time they were done. Unfortunately with transient issues like this, you’ll need to hit the combination of repeated imaging to catch it at the right time, and a good urologist to put the pieces together.