Pretty sure GeckoOBac is referring to the "Thrash-less Rotation" for Shadow/Assassin Tanks. There wasn't much melee to be had in this rotation until the boss hits <30% (for Spinning Strike).
You can't be serious
Thrashless rotation used to go more or less like this:
Shock / Project, Wither / Slow Time, Discharge / Force Breach, Saber Strike, Shock / Project, Force Lightning / Telekinetic Throw, Wither / Slow Time, Saber Strike, Shock / Project, Saber Strike, Saber Strike, Wither / Slow Time, Force Lightning / Telekinetic Throw
So he can't be talking about Thrash-less rotation (which was not optimal BTW, as optimal was back the low-thrash rotation which would occasionally have a Thrash in place of Saber Strike) since even on targets that are not below 30%, even in the completely Thrashless rotation a lot of the attacks are Saber Strikes which does not really match with his claim of them using "exactly zero (0)" melee attacks.
Of course, even the Thrash-less Rotation uses Saber Strike for force management.
The point of using Saber Strike was not just about force management. Of course it is a no-cost attack as opposed to attacks that do cost force, so in that sense it is about force management too, but it does not actually give force to tanks like it does to a dps.
The other purpose of Saber Strike in the rotation was to fill the gaps. That is, it is better to hit the enemy with something rather than stand still doing nothing while both shock and wither are on cooldown and you still don't have full 3 stacks of harnessed darkness/harnessed shadows.
The post 2.0 rotations still follow for the most part same basic idea.
-When less than 3 stacks of harnessed darkness/harnessed shadows a priority is to use Shock / Project and Wither / Slow Time to build up to 3 stacks as fast as possible.
-When at full 3 stacks use Force Lightning / Telekinetic Throw. Never use it with less than full 3 stacks.
-When both Shock / Project and Wither / Slow Time are on cooldown and you still have less than 3 stacks use melee attacks
What has changed is which melee attacks to use, but that's about it. And the rotation for maximum dps/threat might be slightly different now from rotation for maximum survivability/self-healing
Of course Assassins and Shadows could before 2.0 (and still can, although the difference is now much bigger, but before it was only a few percent) actually tank and do enough damage and threat to hold aggro at least against mediocre dps by using only their force powers, but such a rotation would require them to, as I already said, to frequently stand still doing nothing for several seconds while waiting for abilities come of cooldown. While possible, this is of course far from optimal.
Other alternative for a rotation without melee would be to use Force Lightning / Telekinetic Throw on cooldown as often as you can, but that is definitely the stupidest thing a shadow/assassin tank could ever do, as its cooldown is much shorter than the time it takes to build up to 3 stacks and you would end up using it on 2 stacks which is just the worst mistake you could ever do, as it does not heal you at all without full 3 stacks. So you would loose all the healing from your most important self-healing ability, which makes up for 80-90% of your self-healing, making you the worst tank ever.