There's no such thing as a “single shot semi auto”.
“Single shot” means that the gun only holds one round. You load one round into the gun, fire it, then you have to load another before you can fire again.
“Semi auto” means that the gun has a magazine that holds multiple round,s and when you fire it, some of the explosive force of the round is harnessed to work the action, to eject the spent case, and load the next round into the chamber, and set the gun up for the next shot.
In between those two is a “repeater”; it has a magazine holding multiple rounds, but between shots, you have to work the action to set it up for the next shot. A pump-action shotgun is a good example.
All of these guns are semi-automatic. Pull the trigger once, and the next shell if ready to fire.
Technically, a revolver isn't really considered semi-automatic, though in practical terms, a double-action revolver might as well be.
I do have a gun to which the term
“single shot semi auto” could be stretched to apply. It's an old Savage .22 rifle.
With the bolt locked open, it's very easy to just insert a round by hand, directly into the chamber, so you could just leave the magazine unloaded, or even leave it out altogether, and operate it as a single-shot.
Or, you could load the magazine up, work the action,and then leave the bolt locked closed, and operate it as a repeater; between each shot, you'd unlock the bolt, work the action, then lock the bolt again before the next shot.
Or, if you load it up with .22LR rounds, and leave the bolt unlocked, it operates as a semiautomatic.