THR dropped this news, reporting on what went into the final cameo that teased a new Batman. According to them, there were a lot of moving pieces/re-shoots that went on right down to the wire ... with the final scene being reshot in January to include the character people see at the end as the "new Bruce Wayne." Spoiler ... it ain't BA or Michael Keaton.

Apparently, the ending underwent 3 different iterations before landing on what people saw in theaters. First -- when Warner Bros. was still part of AT&T -- the final scene was going to feature Ezra Miller's Barry Allen seeing Keaton's Batman and Sasha Calle's Supergirl.

After WB merged with Discovery, however, a couple of new lieutenants tweaked that a bit ... to include Cavill's Superman and Gadot's Wonder Woman -- in addition to Keaton and Calle.

This 2nd iteration came together when WB still thought Cavill had a shot of reprising the iconic role -- which was spearheaded and somewhat cemented by The Rock/'Black Adam' last year -- but got completely undone when Gunn came onboard as the new DC chief.

When Gunn was hired, THR says he completely scrapped the new ending which featured Gadot, Cavill, Keaton and Calle -- and, instead, opted to insert a former Batman actor as a little nod to the canon ... George Clooney.

The reported rationale for this is that Gunn and co-DC chief Peter Safran didn't wanna give fans of the Snyder-verse any false hope about these characters returning in their new revamped universe ... so they got rid of the two cameos at the end and went another way.

Here's what's strange about this ... while Gunn and Safran might've nixed Gadot from the final scene -- they still allowed her to make a cameo earlier in the movie. And ditto for Affleck, obviously, as it'd been well-known for quite a while that he'd be in this flick.

So what we're getting at is this ... it appears there was selective casting for 'The Flash.' Gunn and Safran were ultimately cool with Gadot and Affleck getting some screentime (if not for the last time) but for whatever reason ... they don't seem to have been okay with HC getting a final bow as the Man of Steel. This looks to be backed by their huge about-face with him.

Now, the question ... what might Gunn and Safran have against Cavill, who really appears to have been screwed out of the DCEU in this transition? In reality, probably nothing, but what's become evident in the past few months is that Gunn has his sights on a new Supes.

The new DC head has already said he's starting his new universe with 'Superman: Legacy' ... and due to that, it tracks that he'd wanna lose any trace of Cavill's Superman as soon as possible. In fact, if he'd been hired pre-'Black Adam' -- you could argue he likely would've nixed that whole post-credit cameo ... which, in the end, amounted to just fan service.