Its the same file, epic just runs it through a script before dropping it into the UEFN editor. The only thing that actually changes is the materials setup. Epic explains this in their YouTube video about metahumans in UEFN.
The decreased file size is there in ue5+ & the blueprint component can be recreated easily by calling the post process anim bp and changing exposed variables on the corrective bone nodes.
This and more can be read in my post covering the topic: