It doesn't look like there is any disagreement about being able to do one-handed racks. And normally the easiest
way to do that is by using the rear sight. Seems like the folks who make and sell sights could come up with a rear sight design that is 'smooth', but accomodates this ability. Maybe not. I'm not a design guy, after all. And it's a sure thing that somebody
wouldn't like it.
On the other hand, real world, if I thought I might get into a gunfight and I didn't/couldn't have a rifle, I think I'd just be ready to do a New York reload with a wheelie or something. Which is one advantage of that design in this respect. (One-handed operation, that is). But this plan requires twofers with a wheel gun BUG, which isn't always an option. One still needs to practice and train for all eventualities. Unfortunately, Murphy will almost always tap us on the shoulder at the most inappropriate time.
Edited to add:
That got me thinking about what I did on the street way back when. I had a Model 15 duty gun and a Lightweight Commander BUG. Applying my own logic, that should have been reversed. But you do what your agency tells you to.
Besides, I would have had to run out of ammo for the 15 (under most scenarios) before resorting to the Commander. And that (running out of ammo) was a low-probability at the time,
because my particular situation made extended fights unlikely, and I carried way more full speedloaders that I thought I might need.