The "key" on the bearing shell is not all that keeps the shell in place in the rod.
A properly sized/finished rod big end bore is smaller than the OD of the bearing shells resulting in "crush" of the shells when the cap is installed and tightened--this also REDUCES the bearing ID to the proper size for the selected journal size. When crush is reduced the bearing/journal fit is made looser-also the shell is not secure in the bore and will shear the key and spin the shell destroying the journal because the oil supply is cut off.
A bearing that has spun in the bore destroys the dimension as well as the smoothness of the bore, and since the soft part of the shell takes the shape of the steel back and supporting bore,now the part contacting the journal is not uniform.
Even small particles trapped behind the shell at assembly cause a high spot in the soft layer contacting the journal and can cause premature failure.
The size/finish of the rod big end bore is CRITICAL to bearing life.
Question : why are you so opposed to pulling the head/piston/rod to make this one right?
