[belatkuro]

That was only the anime. The LN didn't even mention the words "Nerve Gear". The details that Haru researched just described it as a headgear-type VR machine.

Spoiler for vol4, ch8:

A VR device that wasn’t a Neuro Linker. They certainly existed. In the 2020s before Haruyuki was born, there should have been huge headgears that were equipped to the head. But, the machines of those days were only for Full Diving, and the Neuro Linker should have been the first device that had an AR (Augmented Reality) function which allowed for a virtual desktop to be operated while moving around in the real world……

Though the release month for that technology in AW coincidentally matches the release month of the Nerve Gear in SAO.

Spoiler for SAO vol1, ch2:

Half a year ago, this machine (which started selling in May, 2022) successfully created a «Virtual Reality». The electronics company which created the Nerve Gear called the actual act of linking to the virtual reality...

Spoiler for AW vol4, ch8:

The first headgear-type VR machine that implemented Full Dive technology was marketed in May 2022

Take that however you will I guess.
Still on the side that says they're not connected.