If you’re a professional shooting 4K 60 ProRes video you likely have the budget to upgrade the storage (or shoot with a real professional grade camera.) it’s highly unlikely you could have a good user experience with 128GB (minus the OS and all your other personal garbage) filling up in minutes shooting in this mode. The lower capacity models aren’t designed for those specific use cases in mind, and it’s cool they’ve found a way around that limitation through the use of external attached storage.