Yeah, I only worked in the business shortly but I would dispute that statement as well.
Back at the time licensing from iD was basically "here's a cd, never call us again." Meanwhile Unreal, at a much more approachable price, also came with support contacts, a private email list and irc channel, etc. It was like night and day between the two.
In my role as a level designer I vastly preferred UnrealEd. The workflow was more interactive, and the BSP implementation way more robust against leaks. There were flaws to Unreal... the initial versions of UnrealScript were not great. But again, there was simply no comparing the two imo.