That's very interesting. Having only been 4 when Code Veronica released, it's been really hard keeping up with its development as I've heard so many conflicting things over the years that makes it rather unclear what the "real" RE3 is and thinking about it now, that whole discussion has really derailed me from ever learning anything about Code Veronica's general development. Having finally played it now, just from a design and technological standpoint, it really does feel more like a true third entry with how they evolved the fixed camera and dual scenarios.
But that trailer definitely does give me the same vibes as the reveal trailer for Revelations which was released when the game was only 20% finished and I think it was even confirmed that it was nothing more than a mock up trailer to give a general idea of the tone and direction they were taking. So it wouldn't surprise me if the same ended up being true here. I guess they could have been describing an early version of Alexia.
You make me feel old, man. Hopefully, I won't last for long, so young people telling me they were little more than babies when certain things happened will not be a concern anymore.
Anyhow, the real RE3 is a game nobody ever saw: it was put in development after RE2 and was produced by Hideki Kamiya. It starred Hunk (from the 4th Survivor minigame) and was set on a cruise ship infested by zombi-plant hybrids. You can see some concept art here
https://www.crimson-head.com/crimson-head-elders/nakai-zombies. The game was slated to be released on PS1 but, when the PS2 was announced, they decided to migrate development on the new system. Since Capcom owed Sony a "Resident Evil 3" for the PS1 by contract, a spin-off titled "RE 1.9" (or Gaiden or 2.1), starring a team of UBCS soldiers trying to escape Raccoon City, was promoted to mainline entry with the addition of Jill as the lead in order to make it feel more legit.
The "other" RE3 became RE4, only to get completely scrapped in favor of a new version directed by Kamiya and starring superhuman Tony Redgrave searching the castle of his father, Umbrella founder Ozwell E. Spencer. This game eventually became "Devil May Cry".
"Code: Veronica" is in a strange position - it is a mainline game and it's the true sequel to RE2, but it bears no number in the title. It was created after Capcom told SEGA they couldn't successfully port RE2 on the Saturn, so they all agreed to make a new RE game for the then-upcoming Dreamcast. It was never supposed to be RE3. Shinki Mikami in an interview said it should've been a numbered entry - and I agree (even though the non-numbered title sounds great) but, given how everything was set up, the only available title would've been "Resident Evil 4" and, back in 1999, that was unthinkable, since the series was born on the Playstation and that's where most of its userbase was. Not to mention the fact that "RE4" was confirmed to be in development for PS2 pretty soon afterward. Mikami notoriously didn't like the Playstation 2 and he eventually made that famous exclusivity deal with Nintendo a few years later, but, back in the day of C:V, they would've prevented him from doing so (SEGA was clearly on its last leg). In order to keep everything simple, they should've made the Dreamcast game a true spin-off (the "Hunk-on-a-ship" scenario would've been perfect, actually), but instead, they made a full-fledged sequel. When you really think about it, Code: Veronica would've been perfect to release as RE4, even though Mikami and pals wanted something "completely new" and C:V is still classic RE with some minor upgrades.
