It has a point though. It stems from the 10H service which was an igo service which replaced parts of the 8A/C service around Monument Lane and also provides a reason for a decker to be able to be on the X20/1/2 peaks.
The only reason a decker is used is because it goes onto the X20/X21/X22 afterwards in normal times. It runs out of service to Woodgate after terminating at the QE to commence an X22 to the City Centre.
The 25 never would need a decker, so I don't see how it provides a reason for a decker to be able to be on the X20/X21/X22 peaks. And presumably the decker wouldn't be used if it didn't go onto the X20/X21/X22 afterwards, since its the X20/X21/X22 that require deckers. Many times when I used the X20/X21/X22, the deckers used to have full standing loads after picking up from the University North Gate stop in the PM peak.
Infact before the 10H went onto the X20/X21/X22 afterwards, the 10H was always operated by single decker B7RLE.
It does connect Monument Road in Ladywood to the QE and City Centre. But then again the Hagley Road services and 80 also operate at either ends of that road (Its only a relatively short road) frequently, so most would walk to one of those services I think when going to the City Centre. They are high frequency and operate all day.
And I agree hardly anyone uses the 25 (or previously the 10H) from what i've seen.
Discount Travel Solutions/RK Travel run in competition with NX on the outer circle. They run infrequently and at odd times.
Not a pointless service though, the Outer Circle is a very heavily used key route, most use NX.
DTS/RK Travel do carry passengers though. Largely passengers who are paying for single tickets/N Bus and get on the first bus that comes, no matter who the operator is, or concessionary pass holders. And where delays they pick up people who pay 50p to get on with NX passes, and delays are not uncommon on the Outer Circle.
Currently their service is suspened due to COVID - 19. And only NX are running it, so I wander if/when they'll come back.