The fact about Xavi Alonso is he is still a young coach and he is not experienced a lot which means this coach can even have better performance if he gets experienced and starts working in some other teams.
Maybe that's a good reason to say other teams like Real Madrid and even Bayern Munich are going to show even more interest in hiring Xabi Alonso soon.
If I'm not mistaken, Xabi has said on several occasions that he is currently only focused on Leverkusen. at that time, when he was linked with Real Madrid to replace successor Carlo Acelotti. He said that he was still not suitable to coach a team that big. which means, as you said, Xabi still needs more flying hours to solidify his career in coaching.
That's why this former Real Madrid player, who is also a coach, said this.
Honestly, if what I say is not wrong based on the source of the information. Xabi's answer was very cool even though it seemed more dipomatic. But apart from that, Xabi realized that he still had a lot to explore regarding his coaching experience. Moreover, his current focus is solely on Leverkusen and how far he can take him. Maybe, Xabi prefers to start from the lower level. and it could be that the case that happened to Nagelsmann made him a good example for himself. and what is certain is that his current focus is only on Leverkusen. He has brought him this far even though they haven't challenged many big teams, but Xabi has shown his expertise as a coach.