It looks like a false positive (?!)
If I write this code, prefixing each option with "T1 " to check that I'm really using it, I and that I put it as an image for you to see the highlighted error on communes:

You can see that Type Commune[] must have a [Symbol.iterator]() method that returns an iterator. is really considered as an error,

But what is troublesome, is that it doesn't prevent Angular 20 to compile the application and is working, whatever.