As far as I understand this, there are two considerations, and they are almost never dealt with directly.
One, is the Loading Density for the Charge of Powder and Powder Type being used for the weight of the Bullet and the depth the Bullet is to be seated.
Two, is the location of the Crimp-Groove in the Bullet, and, these can vary from one Bullet make or model to another as far as how far they are from the Bullet Base, thus effecting the Loading Density.
Maybe there is a third thing, which is that one would probably want for the Cylinder to still be able to rotate once Loaded with the Cartridges, and too much OAL could interfere with that.
So a stated OAL for a very specific Bullet, is another way of taking into account a presumed complimentary Charge's Loading density, for that Bullet and it's weight and purpose, as well as how that was broadly anticipated in the Bullet's design for it's Crimp Groove location.
I think if one really pays attention to all this, it gets very interesting.
So, as far as my own over-view or acceptence anyway, for Revolvers -
When trying to compare somewhat different shape Bullets of similar or same weight and both are Lead, or, both are Jacketed...where one has technical Loading data for the one, but not for the other, it is really the Seating Depth one would be interested in respecting directly, rather than to respect it indirectly, by working for a same OAL.
