If I was consulting on a flat fee, that's the advice - virtualize to the most compatible OS - I'd typically offer because it is the most likely to deliver the most business value over the long run. On the other hand, if I was charging by the hour, I'd spend my time and the customer's dollars creating a one-off installation that is likely to break and need future $upport when components change.
On the third hand, if the task was trivial, then there would be no reason to complain about a lack of bespoke Windows instructions, since they would almost write themselves. Of course if bespoke Windows instructions are non-trivial, then obviously it's hard to see merit in the complaint.