Letter vs Spirit
The ball didn't appear to move, certainly wasn't obvious after the shot. Shane could have warned Johnny it looked like his shirt had touched the ball. Perhaps some past history of nitpicking on Johnny's part, Shane called the foul. Johnny could have denied the foul and that would have been the end of things, no ref. Instead Johnny accepted the foul.
That sound like the right approach.
I am not a lawyer (or as Jim Carey would say “liar”) but in Law 101, this is letter vs spirit of law situation.
Strictly applying the letter of the rule , this is a foul on a technicality (shirt touching ball) but the spirit of the rule (i.e. ball did not move) should be applied here and this be deemed as no foul.
Calling on a technicality is not uncommon in other games/ sports . In chess, there is a ridiculous “touch-move” rule. If you accidentally touch one of your pieces in chess , your opponent can apply the letter of the rule and insist you move the piece on a technicality even though you do not intend to move it.
If whatever this version of the rules is anything like all ball fouls, it is a foul to touch the ball whether it moves or not. You see it called regularly in snooker events and in properly refereed pool events from Europe (like the Matchroom events). So to me it’s a foul and should be called as such.
Now if it is some version where the ball has to move before it’s a foul, then it doesn’t look like a foul to me.
By the way, I was just at an event here in Toronto with Stephen Hendry and Jimmy White and local legend Cliff Thorburn. One of Cliff’s stories was Cliff being on the hill against Jimmy in a final of a major tournament and Jimmy calling a foul on himself that nobody saw. Cliff ran out and that was that.
Jimmy White has always been a real gentleman. Maybe that is why he failed to win countless World Championship finals. LOL