I think we are talking about the same thing. Imagine you remove the bar so the Bb no longer tilts. When you press C# it will go behind the plane of the Bb making it impossible to slide onto it across the roller. You'd have to either lift your pinky to get to Bb or keep the tip on the C# the whole time and pivot your hand down to press Bb with the side.
How did players get along without it? Well they had to do one of the things above, lift or pivot the hand, neither of which is ideal. The leverage from the side of the pinky tip is pretty weak.
I dunno, I mean everyone has their take on things I just do not think that depressing the C# without the tilting Bb makes it "impossible" to slide. To me that's an overstatement.
That is what the roller is for, the way I see it. As long as a portion of roller is below a portion of the C# touch, I can get my pinky to 'slide' if you wanna call it that, down across the C#, to the roller of the Bb, which at that point begins depressing the Bb, then my finger rolls onto the Bb touch. It doesn't seem un-fluid at all to me.
So I would still argue that one need neither "lift or pivot the hand" on a BA style table at all, actually.
The only instance where I can see what you describe and feel it 'impossible' (or just odd), is if the G# touch doesn't have enough cork on its underside so it depresses down really far, which would take the C# down far with it... and create a larger gap/travel distance to the B roller. (IOW the C# cup opens quite a lot - more than it needs, thus the C# touch depresses a lot, more than it needs to).
That is something which should have been properly regulated out of the factory, and if it wasn't (commonly it isn't especially on budget/student horns, also on horns which have gone thru a whole bunch of "do the minimum to keep it playing servicing over the years, without somewhere in there really getting a nice re-reg along the way) then a tech should have corrected that. The C# keycup need not open much at all to get a clean C# to speak. If that is set correctly then again it feels fine, IMHO.
Anyways...different strokes. I hear what you are saying, I just have never had a problem with response or speed on a BA style (used on so many contemporary models up until pretty recently) table...and truly can say around 66-70% of my beyond-beginner customers don't really care whether the tilting mech is there or not.
IMHO, the true 'revolution' in the table from Selmer came with the changing of the hinge directions and the aligning of the Bb nicely below the C#, with a roller there too. What came next oin the VI has always been to me a "OK, I can take it or leave it" change.
The only vintage table I can think of that really examined that situation and made it the BEST a vintage table could ever get was the 10M and 6M, which actually have a diagonal roller below the C# to make that transition nice and smooth. As others have stated before, those tables were probably 'as far as a vintage table could ever go" as far as fluid transitions.