Holiday hours are just overtime hours that are approved by default, even if you're under 40 for the week.
If you work 8 hours on a qualifying holiday and 32 hours the rest of the week, that's 32 hours of normal pay and 8 hours of overtime pay.
If you work 8 hours on a qualifying holiday and 40 hours the rest of the week, that's 40 hours of normal pay and 8 hours of overtime pay.
Anyone in leadership that doesn't understand this shouldn't be in leadership, especially if they're HR. That said, it all still falls into the same bucket of payroll. You could work 24 hours on a holiday and 40 hours the rest of the week and be just fine because you're not getting unapproved overtime, but you're still working 64 hours that the store might not have allocated for you. That's the only reason why leadership may not want you to work over 40 (and maybe some labor laws depending on where you live).