Not sure that's the case
For one thing the CL/EL has expanded to include extra games in January. The other thing was that Celtic IIRC were usually well out of Europe by late November (in that the remaining game(s) would be dead rubbers)
Celtic were in the group stages of the CL that season and so the only difference in no. of games there would have been the additional 2 that have been added to European group stages. No point talking about dead rubbers as we pretty much rotated fully in the early group stages so no real difference overall and doesn't really matter in the context anyway.