Not the Exandria Unlimited nominator, but I always nominate it as a separate fandom, and I was planning to do so here as well. I have a mix of reasons for this, some more personal and some more general, but I can't speak for the nominator's thought process. The tl;dr is: I view the relationship between CritRole and EXU more like the relationship between the Law & Orders and Chicago Fire/Med/PD than the relationship between Stargate SG-1 and Stargate Atlantis.

* EXU is fully standalone, in a way that not all shared universe cases are. You can watch and understand it knowing absolutely nothing about previous campaigns. References to things from previous campaigns are fun in-jokes for the players and long-time viewers but they're just regular old history/worldbuilding for the characters in their own world and new viewers. There's almost no character overlap, and, when character overlap does exist, the characters are played by someone else (Aabira as opposed to Matt or their former player). It may not count as 'different versions' of the characters, but cast members have, in the past, talked (very politely!) about how they don't recognise certain elements of their characters when Matt has stepped in to play them.

* Critical Role in general is a weird case for shared universes, because it's a universe that's meant to be shared with, well, anyone, in a way that most pieces of media aren't. 'Takes place in the same universe as Critical Role' describes a huge amount of potential fandoms, and (this is admittedly thinking ahead a little bit) you'll eventually have to decide what makes something 'Critical Role'. That Matt is the DM? That Matt plays somehow? That an original cast member is involved somehow? That Matt said it was canon? That it takes place in Exandria? Etc.

* I prefer it as a requester: I straight-up DNW campaign 2 characters or canon in my EXU requests. While I feel very comfortable doing that in an EXU request that signals its narrowness from the start, I feel like I'm being a bit of an arse to potential creators to request EXU characters under Critical Role and then DNWing references to more than half of Critical Role. Requesting EXU characters under EXU also is a very clear signal as to the time period I'm interested in (e.g. these characters at this point in time 30 years post-campaign 1) without me having to write even more DNWs/optional details.

* Very personally, EXU is way shorter and has way fewer characters. It can get lost in tagsets and requests when it's dropped in with the main campaign.

Sorry for the wall of text!

While I sympathize with your desire to keep them separated, Femslashex has a very broad fandom combination policy - we separate related fandoms if the person requesting Jane Doe in Critical Role would mean a completely different person than Jane in Exandria Unlimited. Given our prior policy, we're going to combine Exandria Unlimited with Critical Role. You're welcome to DNW various campaigns in your Critical Role request! It's definitely not rude given how Femslashex combines fandoms, and we'll enforce it.

Thanks for the explanation. I do consider them potentially different characters because of EXU's standalone status and don't request it when they're combined, though.