It doesn't say UNS. It says NS. There is no 17 pitch in the old American Special threads. It took exctly one web search to find the old standards, which haven't been in machinery's handbook for who knows how long. For that matter, 17 pitch isn't in the Unified standard either.
If you decided to make a 13/14-17 thread in your shop, go right ahead. If this is a "not my problem situation", that really doesn't help things along. It should be as obvious as stubbing your toe first step out of bed in the morning. 50 years ago if you had to sit down and calculate the diameters (disregarding the additional call outs) to produce this thread, you would have stopped and thought about it. Even if you did that, how many manual lathes(dating to the spec's era) have a 17 pitch thread feed? Today, you plug it in here or there, or ask online and someone with no skin in the game does it for you, and CNC makes whatever nonsense you program.
Anyway, I hope OP comes back with an answer from the customer as I am curious.