Sounds most likely. It's a form of "inventory circumvention", but UA search is doing the dirty work for you (so they can't really go after you like they can after agents).
Here's a discussion of it on DL Pro website where they seem to have been having issues with some agents doing it -- https://pro.delta.com/content/agency...-version-.html



Married segment inventory (only U bucket open) with a one-way search



Individual flights inventory (inventory availability as low as T) with a multi-city search