HomeKit appears to be renaming my AirPort speakers even when the Home app is not set up

My daughter managed somehow to rename the AirPort speakers in our bedroom while setting up her new HomePod, so that now our speakers are called “[Daughter’s name]’s HomePod”.

I went into the AirPort Utility to change their name back to the original, but AirPort Utility says that the speakers are being managed by HomeKit and that I need to use the Home app to rename them.

The only problem with that is that they don’t appear in Home, and indeed they wouldn’t as AirPort Express long predates HomeKit. My understanding is that they cannot be added to a Home setup.

I deleted my home setup from the Home app, and then it appeared I was able to rename the speakers. However, the next day I noticed that Home had apparently renamed them again, even though there was no home set up!

So far, the only way I can prevent the Home app from renaming my AirPort speakers is to completely delete the app. If I reinstall it, the problem recurs.

Where on earth is the HomeKit data that remembers this erroneous setting and keeps on trying to reapply it even when there is no home set up?