A friendly match with the main squad will obviously pose a big risk, because after all it will only have the potential for the main players to get injured, but even so, of course there are bigger reasons for kompany to take that risk such as maybe testing new tactics or improving the cohesiveness of the current main squad, but I think he should also need to maintain a balance between maintaining the fitness or mentality from all their players, so that Kompany should also be able to give opportunities to young players or reserves to maintain their mentality, because after all, player rotation is an important strategy to maintain the team's overall fitness and performance.
Bayern Munich are faced with much tighter competition this season so they must try to show consistency in every match and maybe that's the reason why Kompany did not try to rotate in friendly matches so they could find the right strategy format for the team. Injuries were a consideration but that has passed and Bayern Munich players are fine after the match ended. This season is not so easy for Bayern Munich because Leverkusen itself will try to defend the trophy so they will try to play more consistently. Keeping players fit is very important and it is probably true as you say because Kompany must be able to use young players or reserves as a way to maximize their strengths.