I'm not arguing that, I'm just can't see how a wider mouth (with the constant volume) can do the job better. Scoop, compact with a stick, scoop again, compact again... What I'm missing?
In short, I think 3/4 inch is quite a narrow slot to fill... and I'm very confident that the "U" cut version will be more effective.
Making a U-cut at the outward curve side will let you scoop much more effectively because of the wider opening. On hard snow you use it as a carpenters plane iron, all that is "shaved off" goes into the boottle.
And when the first snow is (partially) melted you want to add more snow, using your hand or whatever else you have available for the job. (Snow is best melted in a water/slush mixture, so use the first water as "seed" to melt more snow). Expanding the opening will greatly simplifly the job of adding more snow and compressing it inside the pot.
Perhaps I shouldn't be as persistent about what will work best when I haven't tested it. I am 100% confident I'm correct about this, having done my part of mucking about in the snow and all that. But let's just say I do my bottle my way and I promise to back to tell you if it works out the way I wanted, shall we? If I'm wrong I'm not afraid to tell you, that's just a shared learning experience.