Hi there - take a look at the profile/stats of the player that shot the 53... You will probably find he is lvl90 or higher, legend or tour legend tier - with >2000 ranked rounds. Also, he probably has the best equipment ito spin and distance control.
Also, if the tournament is at BPB or StGeorges, par there is 70, so a 53 is only 17under, so not even a "perfect round". Two players that I know of have shot 49's. One at Kiawah (5 eagles and 13 birdies) and one at Cabo. The Kiawah one was off shorter tees than normal, but the Cabo round was off the tips.
Some people do nothing but play all day on WGT - that kind of practice makes pretty permanent knowledge and skills development which can easily translate into a 53. Stick around, practice, take notes, hone skills and you could get there too......