Samsung Pay is different in that it works by faking out the magnetic strip reader... .in theory it should work with any credit card terminal that you can swipe a credit card (but in reality you come across a few that don't work). I've used it for years and am quite used to clerks telling me it won't work, and then 'Beep' my receipt is printing out.
Apple Pay is software that must be installed on the terminals... if the terminals are not specifically set up for Apple Pay it will not work.
So while Samsung Pay may work everywhere, that doesn't mean Apple Pay will. Although the last year have seen quite a few places have 'Touch to Pay' terminals that advertise both.
Not sure what Universal has done to accept Apple Pay.