Is that response based on the fact that they may not have the data required to perform the task that it would take to make it happen or the willingness to even try?
I have had a station on WU since 2008. My memory may be fading, but I seem to recall some previous mention (when you could actually communicate with them and they responded and had lots of other information on their site) that a deleted station is "deleted". I am presuming that 'deleted' is the same as removed from their site, and their 'Delete' option gives you a chance to Cancel the process or OK.
I don't know if they would still have the information, and as to willingness, again I don't know but from personal experience in asking about things that they did have available or published at one time but then stopped, I would say one or the other.
Under their Personal Weather Station Hardware and Software section the link to Cumulus is still the original Sandaysoft site which Steve Loft, the original author of Cumulus, maintained until his retirement more than 5 years ago. This link now fails "The requested URL was not found on this server". The URL to the current Cumulus site changed many years ago but WU has failed to make the change, nor responded to my emails on this.
Maybe my "Likely zero" should have said "Likely 0.1%".
Enjoy,
Paul