I try my best to match CHIRP up with the capability built into the radio's firmware. I assumed that all of the models with this display supported 7 characters, but I was proven wrong with these so-called 'waterproof' models. But the original UV-5R firmware always supported 7 characters.
The OEM software has never supported 7 characters. I wonder why they'd remove a character from the Alpha Name display? Because it has the same display as the UV-5R & UV-82R, and those display 7, I assumed it did.