Yesm when I upgrade from 50 tot he Fios Gigabit Connection, a tech was needed to upgrade the wiring in my home in order to be able to use the speed.
If not that you might want to call sales and find out more about it.
It is another "below-the-line" fee that Verizon (and all cable/internet providers) use so that they can claim an advertising price yet jack it up with additional fees not put into the advertised price.
In fact you are correct, I was told the fee is to replace the coax curently between the ONT box and my router with network cable. Sounds like a scam to get an extra $99 as people start to want faster internet teirs. I was on a faser tier previously and didn't need any special cable. Now if I want anything over 75/75 I magically need to spend $99 to have the cabling "updated". From what I've read any recent coax should be able to handle speeds well over 1 gigabit without issue. I could see it if they had to replace the ONT box or the router etc.
I didn't really need faster speed but the higher teirs were a pretty cheap upgrade, but if they are going to stack a $99 fee on just to swap coax for network cable that I don't need I'll keep my current plan.
If you currently have 75/75 over coax and want to upgrade to any speed over 100, it must utilize Ethernet. And depending on the model of your ont, that may also need to be upgraded.