There could be differing sound concepts at play...
First note, most of the literature I play is OLD... and I know that means 65% of the divisi I see are accounting for an Eb bass. But they do account for it, which leave open the possibility that the composer thought it might be okay.
Britishers were/are very well acquainted with tuba voicing and that there are different "basses" in the military ensembles being scored for. And in some works the two parts are very different (Colonial Song) and this can be in present day arrangements and compositions as well, much as they are in string bass scoring (Cowboys by John Williams).
Another disclaimer which is probably obvious - I like and often prefer Bass tuba. BUT, this isn't absolute. When we've had a section of all BATs, and one was on top, it DIDN'T WORK. We got the hand... we hated it... we all played lower part as possible. I brought the Eb the next day. No hand, happy section, Damn good band (I still pinch myself that I'm as lucky as I am to perform with them).
I have enormous respect for our conductor, Loras John Schissel. He's also a tubist, so he's... difficult to please. He's a scholar of Sousa at the LOC, and listens intensely to recordings and other information regarding his works and instrumentation (and many other band masters of yore), and his editions of these marches are very interesting and enlightening. Yes, he removes some divisi because that's what he hears. And even changes things (Stars & Stripes - take the trio Eb-Bb-G-Eb lick straight down ONLY!). I sometimes add them back for volume sake if he wants more, or (get this) for clarity... it can de-muddy it (?!?). Truly. And I would be destroyed publicly if he didn't like it.
I'm a part of a whole. Sometimes I play the "one tuba" parts when we think it deserves or if it really is an Eb bass part only. And the four of us, if we're playing something more contemporary, can smell a foolish composer 40 miles away and will fix a part before anyone knows anything... we work together. That is, of course, assuming the Maestro hasn't already found those issues.
There are fools for band conductors (and don't get ME started on CHORAL conductors!!!). And they often don't have a chicken's clue for what the hell a tuba is or what it does. Everything is about adaptation. But divisi can be a great addition... voiced well... to a section.
Finally... I'm in Cleveland. And there's a "Cleveland Sound" that Maestro Szell is still an effecting factor to. Maazel and Dohnyani (sp?) continued it. It's transparency and breadth. And admittedly, playing after the ictus of the stick (pisses some of us off and makes Loras BAT$#@%!). Maestro Schissel has some finer points, but this is fundamentally the Cleveland Orchestra’s town, and literally their Band. So we have come to this voicing over 11 years of this iteration of this band. Other bands copy it locally and that’s just we all do hear 'bouts

So, as always, YMMV.
J.c.S. (who knows of course that as a fan of Eb, I can hear when it's not there and miss it... and few other care ; )