Less than a month before the Turkish League season begins, the players has to warm up with the preseason matches, I would love to see how they would tactically perform, and see if they still have the same attacking approach. Playing against the second level Turkish League shouldn't be a hard win for Galatasaray, I expect them to conquer in good number of goals.
Pre-season matches are good as they give the players the opportunity to be tested playing together. From the pre-season matches, coaches can already gauge the fitness of some of their players and how well the new signings will blend into the team. Galatasaray start of the pre-season is one with a lower team, which like you said should not be difficult for them to win. But I don't think winning a lone is all the coach set out to achieve as the purpose of the match is to actually test the players.