I was ten 47 years ago, which shows you how long this game as been around. When we played it, someone stood behind you, with his arms around your chest, and held you tightly until you passed out. IIRC, you started by bending over so the blood rushed to your head and then stood up suddenly for the "squeezing."
In any event, that method was slightly safer in that the "squeezer" always got tired and let go before death ensued.
IIRC, I didn't think of it as being "pleasurable" so much as I was curious about what it was like to pass out. (Even in those days, characters were frequently "knocked out" after a punch on TV shows.)
But a psychiatrist might take a different view. This "game" does seem to be common among children on the verge of puberty.
(P.S. thanks for the reminder. My eldest grandson is 11. I'm going to mention this to my daughter today.)