Nowhere in the rules or the equipment specifications is any "spot sticker" mentioned. It is not part of the game, according to the rules.
The foot spot is a single point without breadth. It is the intersection of the long string and the foot string. (See the definition in the rules, here: https://wpapool.com/rules-of-play/#Definitions )
That having been said.... On tables with old cloth and for games with smash breaks like eight ball and nine ball, the foot spot often has a crater due to the head ball being repeatedly struck into the cloth on break shots. This often makes it hard to get a tight rack with a triangle. The head ball keeps rolling into the crater and away from the rest of the rack leaving a gap. The "right" way to fix that problem is to take off the sticker, fill the dent in the cloth very carefully with something, such as a glue/lint mixture, and put a new sticker on.
Instead of fixing the crater, the standard way to deal with the problem is to move the rack up the table a little so the head ball is tight. Often it ends up on the edge of the crater pressed back against the next two balls. But that is just a stop-gap measure and not in the rule book. Anyone who quotes such a rule might be referring to a tournament or event on old cloth where the TD said, "It's OK to push the rack forward a little to get it tight," but I have never seen a written rule allowing this.
I think the practice of pushing the rack forward tends to make the crater slowly walk up the table. I've seen tables where you had to rack a quarter-inch high.
I believe the crater also forms because guys are constantly tapping the head ball to get it to stay on the spot.
I’ve seen some old Brunswicks getting recovered and the crater underneath the cloth can be huge.
Lou Figueroa