Loading for Destiny 2 wouldn't be comparable, IMO. For loading into areas, it's tied to your network performance as well as how many players are playing the game. Even when loading into single player missions, Destiny 2 goes through the matchmaking module. So while no actual matchmaking happens, it has to ping back and forth between the local game and the Destiny 2 matchmaking servers. If those servers are experiencing a heavy player load, it will still affect loading into a single player instance.
Basically testing loading and restarts in Destiny 2 is testing the network performance and local storage performance modified by the number of players playing the game. IE - it wouldn't be tell us anything about PS5 IO system compared to XBS IO system.
That said, it could potentially give some insight into PS5 IO versus PS4 IO. Or alternatively between XBS IO versus XBO IO.
Regards,
SB