The BMW wallbox rating is likely the same as other commercial wallboxes – the issue is the type of circuit on which you would install it. In the US at least, electrical code requires that the circuit breaker should only deliver 20% of the maximum load of the breaker. And most home wiring supports a single circuit maximum of 50 amps – if you use a plug-in wallbox with a 14-50 plug on a 50 amp circuit breaker, the maximum it can deliver is 40 amps. Some wallboxes however support 48 amps, but only if hard-wired into your electrical panel (which can be done) – ChargePoint, Wallbox (the charger) and Juicebox units are all capable of delivering 48 amps (if hard wired), and likely so is the BMW wallbox although any information available is sketchy – hence the 48 amps claim probably.
You CAN install a 60 amp breaker and use a NEMA 14-60 plug with a 48 amp rated wallbox for a plug-in setup (which would be very unusual), but that requires rewiring circuits and significantly more expense, and really not much benefit. Most home charging will occur overnight anyway, and you are unlikely to run your EV down to zero daily so usual charging time with a 40 amp delivery will be 6-8 hours -cutting that down to 4-6 hours is not that much gain with normal charging use case, for a lot more trouble and expense, and certainly not Supercharger territory.
An electrician would be a good idea for any of those scenarios, but if anyone was thinking DIY without the necessary pre-wiring, you could theoretically just install a 60 amp breaker and outlet, buy a NEMA 14-60 plug, set their charging unit to 48 amps, and Voilà! 48 amps to your car – violating code with the risk of overloading your circuits and burning your house down. So hard-wiring to your panel sounds like a better route if you really wanted or needed 48 amps – more expensive than a plug-in but a bargain in the long run, with some small disadvantages (charging unit not easily swappable for example).