This “answer” is specious at best, and in line with the current muddy terms in the EULA.
Your suggestion is equal to photoshop laying claim on any work anyone has made with it, or the inventor of the pencil owed back due.
If Unreal is used to output content, that is then LATER TRANSFORMED, tell me, how you plan to uphold that battle in a court.
Any JR citations is a plus.
Cheers.