I think they have been recognizing it for a little over a year if I remember correctly, just not many have been submitted. CGC has been recognizing it as well so there are probably more graded by them.
Edit I lied, slightly less than a year. @eeveeteam did the hard work for us all! Link to the thread where it is discussed: Eevee Jungle Stamp Obstruction Error - CGC & PSA recognizes it!