This have been widespread with the Diablo 3 botting in the last couple of years, people were just copying whole D3 installs to fresh comps or VMs, but the ban rate had not lowered.
Some of the people, who are around since more than 12-15 years, could remember, that Blizzard used to store the real cd key within their game installations - for ex. Diablo 2.
So it do not require rocket science for us to assume that with similar methods, Blizzard could still identify or "label" every unique WoW installation, and if we do intend to start on clean, the worst idea could be to copy our old WoW install folder to a clean system.