i am a PPG certified painter, been certified for over 30 years.
it's not rally the " PAINT" that's the problem. single stage urethane paint is basically all the same product made by different manufacturers with minor variations between them.
the problem is the budget part of the paint. to get the budget part the manufactures reduce the type of formulas and tints. one reason might be why it doesn't cover is because the formula is a converted from BC CC to SS paint. to do this they mix up the BC CC formula and then add significant single stage clear binders to make single stage paint. now the paint is well over 50% clear tints and binders.

i would suggest calling the paint store and check if it's a straight up SS formula and not a converted one. to get a straight SS formula you might have to use a premium product line and not the budget line. the problem with this is they don't freely give out this information to just anybody, you need to be a regular buyer of their products who spends $$$ often.
this is also a problem the other way from SS to BC CC formulas.
also paint manufacturers have cut back on older car formulas to save $$$ so straight SS formulas really aren't in demand and used on current model cars anymore. with stricter VOC laws some tints have been discontinued or modified to comply with the regulations. so even with a correct SS formula the tints aren't what they used to be and coverage suffers.