It absolutely does matter. Not the 3 games specifically, but the 3-4 weeks on the training pitch is the only time all year we will get that amount of time for pep to really instill his ideas into players before it becomes about maintaining fitness over anything.
We've seen instances of players missing that peruod and taking much longer to adapt. Phillips last season missed all pre-season and the start of the season and by time he got fit we were too swamped with games for him to get upto speed. Similarly when we signed ake, he got a lengthy injury almost instantly and barely featured all season.
We typically like to do most of our business early, it's far from ideal if we were to lose 3/4 first teamers from now until thr close of the window and have to replace them in august.