Not to split hairs (or make a strawman), but I'd argue it's not quite as bad as say, making a F2P Mario game where you have to subscribe to be able to jump. That would be a core mechanic to me, this is technically just the UI they are limiting.
But certainly, if you argued that limiting the UI in an MMO might actually be worse than limiting the actual abilities you can use, I'd be hard pressed to disagree. I would say it was maybe the most ridiculous thing I saw on the list.
I'm glad they did something at least.
Well, part of it is that TOR's gameplay is based, for most classes, shitloads of abilities. Even for say DPS BH at its most spammable, you were dealing with a core cycle involving an initiate, primary attack, debuff, stun, aoe, big attack once your primary stacked enough counters on the mob, weak attack while you recovered resource, and emergency resource recover; that's 2/3 of a single bar just for what you do all the time. An adrenal, a medpack, and two activated trinkets, and you're full up.
Meaning that never mind situationals like melee stun/knockback or DoT, or conveniences like hotbarred mount, a F2P player with one bar couldn't even use NPC commands, any of the several heals, emergency hate dump, the "class-defining" 15-minute panic ability, or so on.
It's like making a Mario game where the B-button will let you run, or let you pick up a shell, but won't do both.
Edit: I take that back, HSM and railgun BOTH depend on stacked counters from TRACERTRACERTRACERTRACERTRACERTRACER, single bar is literally not enough buttons for the "just press the button" DPS class to roll a standard cycle with full buffs and a medpack.