You are conflating Internet service speed and mobile generations. I work for an ISP. I hear this all the time. Especially since there’s also “5G WiFi” which is 5 GHz band. People confuse it all, and it’s understandable but still annoying.
My company offers 1 Gbps service. No one is getting confused by that yet, but our modems have 2.5 Gbps Ethernet ports now, and I had a customer that was outraged the other day because “Your modem is only 2.5 G and all my devices use 5G! You need to send me a 5G modem!!” FFS