Bottom line is that it violates the contract you agreed to enter with WN and subjects you to whatever penalties could be levied. Primary would be zeroing out and closing your RR account and prohibiting its reopening. All kinds of other parade of horrible ideas, none of which are realistic or necessary.

Everything comes down to risk tolerance and personal comfort level. WN's souped up software which also catches "impossible" bookings does look at RR #'s, but also has the capability to look at many other bits of data including name, address, IP address, credit card and so on.

As others note, what you can't do is: 1. Do this often (maybe more or maybe less post-pandemic) 2. Check bags 3. Book onward or return segments (which is not an issue on WN as it may be on other carriers).