I agree Finga, a 3 Amp manual circuit breaker was specified and a particular brand was recommended so sticking to the manufacturer's specs is only common sense.
Generally speaking C/Bs & fuses are only for cable protection but I know you already knew that.
Did come across a little snippet a while back, I had a tiny spark when I disconnected my battery & thought I wonder where that's coming from?
I tracked it down to a very small leakage in my rectifier/regulator and a much bigger leakage in my GME radio even when it was turned off.
I rang GME & the techi guy explained they put a diode directly across the incoming power before the switch designed to blow the little 3 Amp? fuse in case of reverse polarity so in that case the fuse also played a role other than cable protection.
Don't get me started about cable sizes, who in their right mind makes a cable then decides to make up their own sizing system?
SWG, AWG, B&S, they may as well named their sizes after animals or something, "Hey you, pass me a roll of Giraffe Twin & Earth".