Oh, that's exactly what annoys me so much. I'd rather not report it than be misinformed.
I think it's the phone. On my predecessor (Xperia X3 compact), the location was indicated correctly.
Is there a solution?

I have never noticed this discrepancy before, but I can understand it. Thank you for pointing this out.
I think that such phone dialling-dependent location information is controlled (possibly via SIM) by the provider and not from the device. I would ask the provider about this.