IIRC that is not the same size at all. Why? Because Gibson, thrifty as they are, could not use guitar necks on a bass (I'm sure they tried though!), so forced to make a long scale neck from scratch they thought what the heck let's enlarge the headstock too.
PS: On a 2007 Firebird I once had, the headstock was definitely smaller (if similarly shaped) than on my modern day TBs.