There is a condition called hyperspermia which causes a much higher volume of semen than usual. I have seen a few vids on porn sites of guys filling pint glasses.
I can well understand that hyperspermia may account for a larger volume. The normal range is supposed to be 1.5 to 5ml so you'd call ejaculating 25ml, i.e. an amount equivalent to a single shot of spirits, hyperspermia.
But a pint? That's 568ml, i.e. about 115x the normal maximum. Then visualise a pint drinking glass and try to work out where that much would be stored prior to ejaculation. If the prostate was big enough to hold even half of that it would constrict the urethra so much it would be impossible to piss. The only thing in that area big enough to hold a pint of liquid is the urinary bladder.
There will be some impressive cum shots that are real and others that are fake but, by the time someone is filling a pint glass, the conclusion that it is fake is inescapable.