How's the rest of the table look? What's the price? If you want tighter pockets you can have a thicker facing added when the mechanic installs it. It's no big deal. Me personally, I like 5" pockets. But to each his own.
The only way a GC4 would NOT have 5" pockets is if a mechanic installed thicker or more pocket facings, or if a mechanic removed the rubber cushions and replaced them with new ones, and left them longer (which is a big job to do). Hardly any mechanic does that, and it looks like your seller knows zero about pool based on where they have the tape measure. Just based on that picture you can almost guarantee they are 5" factory pockets.