Ego Trip ended up being featured on the American complete series DVD set of Dexter's Laboratory, especially in an official press release from Warner Bros. on last year's May. I have a theory about Ego Trip's inclusion on the show's American complete series DVD set:
What caused the movie to be on the USA version of the Complete Series DVD set itself is its availability on Amazon Prime from December 30th, 2022 to December 30th, 2023. Cartoon Network made the decision to include it on the USA Complete Series DVD set after the limited Amazon Prime availability itself.
This theory also applies to Ed, Edd n Eddy and Foster's Home for Imaginary Friends:
Ed, Edd n Eddy- The HBO Max availability of the only produced episode of the 6th season (May I Have This Ed?/Look Before You Ed) is what caused it to be released as part of its Complete Series DVD set from 2022.
Foster's Home for Imaginary Friends- HBO Max showing Seasons 5 and 6 of the series in widescreen is what caused its Complete Series DVD set to have the two seasons in 16:9.
Pretty interesting theory, huh?