If his “laptop” is a MacBook his music/playlists should sync back to his iPhone automatically...the same if he has a Windows laptop and has the “iTunes for Windows” program installed (”re-sync playlists”). Does he make iPhone back-ups to the iCloud or his PC? He could always restore from a prior back-up before the update...(although I have never heard of an iPhone update messing with music playlists for purchased/owned music files). Sounds like it may be an Apple Music subscription issue? Good luck, might be best to call Apple support with details.
https://getsupport.apple.com/solutions
"Thanks for reaching out to the Apple Support Communities! That's a great question you have about what will happen if you cancel your Apple Music subscription. Once your Apple Music subscription is canceled you will lose access to the playlists you created and any music you've downloaded. Also, your music and playlists would not return if you decide to sign up for Apple Music again in the future. However, you will have access to it until the day your subscription officially ends and your purchased music would not be affected. "
My question answered.
Its a windows laptop