He didn't say that though... The whole point is that the abilities he mentioned are for hindering, which is true, not tanking. Tanking in Underrail is for fat shields coupled with high con and appropriate armor. PSI is much more about strategy and situational choices than straight up tanking.
I would define tanking as a playstyle that is heavily focused on mitigating the effects of getting targeted with an attack, rather than avoiding being targeted with attacks at all, which is how glass cannons get through most of the game. According to this definition, PSP is very much an extremaly powerful tanking ability which can render several attacks completly harmless, with the only requirement being taking the psi health penalty and spending anywhere from some to a lot of points on TC. Even a few copies can easily nullify damage that would be much higher than the HP lost to the psi penalty.
Riot Gear isn't be-all end-all tanking solution either. It's strong vs. melee but that's it. In fact there's not a single tanking solution to everything in Underrail, so the point is moot. All builds will mix and match at least one or several solutions to cover all their bases. Even the most dedicated glass cannons still use shields, which are tanking as well.