I also have never had any of my ball pythons (listed in my signature) regurgitate as a result of feeding them two mice on the same feeding day - some adults even ate three or four.
Pet store employees generally aren't known for giving the best husbandry care. My so called pet store "expert" told me that there are no female ball pythons available in the pet trade, because breeders won't sell them. Told me that I should feed in a separate enclosures or else I'd be attacked by my snakes, told me that I would sterilize my ball pythons if I sexed them.
Forty years of experience he says. And yet they keep multiple balls in one enclosure, can't get any of theirs to eat, have mites, and stuck sheds.
And no - I'm no expert, I just know that eating two mice at one sitting for a juvenile or adult is not going to cause a regurge.