Interesting, I thought it was the same everywhere. Where I live, sites can easily tell when my number is a VoIP or not.
I don't think I managed to find one site that would accept a VoIP number. Google, Discord, Twitter, Azure, OpenAI, etc, all want real numbers.
VoIP when I tried it around 2 years ago, so pretty much useless.
I'm holding out for some company to do an OLED one, or at least for an OLED mod to be available
I'm not sure how it works, but if you look up VoIP/burner identification, there are a lot of services that offer it.