Yes, preseason gives a coach the opportunity to use different tactics and different players so that he can figure out the right tactics he will fully adopt for his team and the players that will be his starting eleven, so we should overlook Bayern Leverkusen's preseason results because Erik Ten Hag is using Bayern Leverkusen's preseason matches to figure out the perfect tactics he will use at Bayern Leverkusen when the new German Bundesliga season starts.
Preseason results shouldn't be used as a benchmark for a team's strength, as all teams still have time to make changes before the next season resumes as usual. So, we should all just enjoy the preseason matches as casual entertainment, as every coach will undoubtedly provide the best guidance for their players when they see their preseason results are so poor. And even teams that win in preseason will still make changes for the better, as they have no guarantee of success in their respective domestic leagues next season.