All of this depends on whether you shoot ATA (Amateur Trap Association. ATA originally meant American Trap Association, but the name was changed in 1923) or Olympic Trap (often referred to as Bunker Trap or International Trap).
Olympic Trap rules are strict and no exceptions are made. For example, white shoes (provided they’re not open-toe or sandals) are allowed, jeans are not. Semis are also not permitted. The rules go on and on. Stuff you wouldn’t even anticipate such as when leaving the 5th station, the shooter must remove all shells from the gun, fired or unfired, and rotate clockwise (to your right). Penalties are assessed for failing to do so and the shooter can be disqualified altogether for repeat offenses. The rule book is so long, I could go on ad nauseum, but you get the picture.
Amateur Trap rules are much more relaxed even in competition. Without a doubt, most folks at an ATA field are there for some fun, but even ATA competitions are more serious about the rules.
Regardless of whether you ask an ATA Trap competitor or an Olympic Trap competitor, they will both tell you the same thing - mindset, stance, mount, etc must be as close as possible to identical for every shot (including in practice) in order to achieve the best scores per your abilities. You can’t achieve consistently high scores when all the variables are different for every shot.
The guys who seem anal over horseplay and shells flinging in their face may simply be there for serious practice. On the other hand, if they’re not competitors, they’re just Karen’s without a cause.
If you never expect to shoot or even try Olympic Trap, a semi is probably fine. You would be limiting yourself to Amateur Trap, though, and even there you wouldn’t be making any friends.