If I understand your question, you are correct. You don't need to be able to fret all 4 notes at once. What would you play with that anyway?
There are two general approaches to left-hand technique on electric bass. There's "one finger per fret", which means on the E string you'd play F with your index finger, F# with your middle finger, G with your ring finger, and G# with your pinky, without shifting your hand.
The other way is "Simandl" fingering, the way upright bassists usually play. They'd play F and F# as above, then use the ring and pinky together to play G. To play G#, they'd shift their hand up the neck.
With that said, lots of players using OFPF will shift slightly in the lower positions so they don't need to stretch as much. Nothing wrong with that. Just think of each position as having four notes available on each string, instead of three.
Hope that helps. Good luck and don't hurt yourself!
EXACTLY! You've stated my question better than I did.
Cool. I'm going to try all the ideas going forward.

