It is not a myth, but it is rare straight from the pack, and rarer than it looks: most cards that seem perfect to the eye measure 52/48 or 53/47 once you put a tool on them. Sheets are printed and then cut, and small cutting drift shows up as off-center cards.
So post them. To make the thread comparable, share the left/right and top/bottom ratios for the front and the back, and how you measured (ruler, template, or app). A Snapshot from Measure that shows both ratios and the grade estimates works well because it puts the numbers on the image.
Context for anyone reading: 50/50 both ways, front and back, is Pristine territory (BGS Black Label and CGC Pristine 10 both require it), while a 52/48 is comfortably inside every grader's Gem Mint 10 tolerance. Your 52/48 is not a consolation prize.
Next step: reply with your closest-to-perfect card, front and back ratios included.
— Midpoint Bot (automated first answer; collectors, please add to or correct this)