More skills allows for more variety without risking balance. Splitting Automatics down the middle like that would play havoc with the inter-skill balance, which is of course not good. Conversely, what would be the purpose of its removal?
Flip it around and look at it again. More skills equals:
-Less Utility per Skill (range of options gets diluted by each additional skill that the options are split between)
-More Optimization Issues (People will usually just spend their points in the skill that allows them to do the most. This is the issue with Automatics currently.)
-More Karma for Generalists (Each additional skill that options are divided into costs a large amount of resources to possess.)
Now take a look at what other attack skills cover:
-Spellcasting covers everything from combat and offensive manipulation spells as well as all others. It certainly isn't split between different categories.
-Blades covers everything from that knife to a claymore.
-Clubs covers everything from a rifle butt to a splitting maul.
-Gunnery cover any mounted weapons.
Yet guns are split into not one, not two, not three, but four different skills. I fail to see how eliminating one is causing a balance issue, because currently it seems like the mass amount of them is the balance issue. Most sammy types just choose one or two and go with it because of the current issues.
Automatics removal would:
-Make weapon skills less arbitrary (rather than pretending that BF/FA modes matter for skill classification).
-Allow the Firearms skill to actually cover all firearms (by folding Heavy Weapons into the skill group in Automatics place).
-Lower the cost of being a firearms generalist, opening up more utility to such characters.
-Cause less optimization issues (since there is no single skill that covers short concealable weapons all the way to long range marksman rifles).
But then you have the issue raised by the post my quote is taken from, if you put a folding stock on a pistol or machine-pistol, do you then have to use Longarms?
Even in those situations, the stance and sighting is a little different. Absorbing the recoil from pistol rounds is a lot easier than absorbing the recoil from rifle rounds. Similarly stances for using pistol gripped long arms are a lot different than stances for using pistols and the like. The Pistols and Longarms skills would cover using those stances in the right circumstances no matter which stance you're using for the appropriate weapon.