Hooking up a 50A hot tub breaker to a 60A subpanel
@Steven is essentially right.   What has been explained many times on this site is that there is NOTHING dangerous about what you propose.    The 50A breaker will be protecting the wiring to the tub (and internals of the tub).   The 60A breaker is protecting the wiring to the subpanel (and its internals).    You can do this if you want and you will be perfectly fine.   BUT, if the tub really does pull 50A and you have it on at the same time as other devices in the garage which are taking more than 10A then the 60A breaker will trip.

Bottom line:   You can have as many breakers as you want totaling more than their main/subpanel breaker.   It is safe.   It just will trip if you actually consume more than that at any one time.   You have to figure out whether that situation will ever occur.