This was briefly a popular(snake-oil) thing for great abs. Stimulating a contraction isn’t the same thing as a muscle be loaded as in weight-lifting. This might be different with a relatively week muscle like the BC, who knows? Obviously you can’t do any weight lifting with your BC.
Supposedly this is what Bruce Lee used on his abs and they were ripped.
I’ve also heard that things like this are used for physical therapy so I’m not sold that it is snake oil, anymore than PE is, I know it doesn’t replace excersizing but maybe it could help? I know I for one have tried to figure out where my BC is and haven’t yet. so if I could stimulate it and figure out where it is I’d be happy.