It more about ticketing systems / GDS -- the industry system for this requires everything to be the same for each passagner on the PNR, same routing, same fare class, same flights (date and time), .... It is the way the system is designed to operate. (BTW, it is a very old system, but it is the backbone for making reservations)

What you saw, the ability to buy multiple tickets once the fare class is showing only 1 ticket is actually left not a common result IME. But there is a lot going on n the background concerning fare class inventory.

I think it is a little earlier to be jumping to pricing discrimination based on a single set of experiences.