This is half correct.
Half correct bit: the build outlined is a basic endgame build, i.e. starting to do Veteran Rank (VR) content. He can already get more than enough Magicka from gear, enchants and buffs to hit the soft cap/Overcharged (orange stat numbers).
Half in-correct bit: he is not even trying to come close to "breaking" the system. He is using perfectly ordinary level 50 gear (though I believe he may be in a PvP zone so getting some Health buffs). It is just how the diminishing returns/soft caps work in the game.
I mean, think about it,
1. Every time you level up, all stats increase anyway.
2. When you stop levelling, i.e. in endgame, all further improvements in your resource stats will come from gear and enchants and should increase to scale up with content difficulty because Max of resource stats affects damage. If they DON'T scale up, that leaves the only remaining stat to scale up, i.e. Health, to increase survivability to match the scaling content.
3. So, for the purpose of endgame fighting the hardest content, the only thing that is unlikely to increase much is Health(*). Therefore, you want as much Health as possible on all classes.
4. Gear itemization is even across all three stats.
5. Attribute points while levelling give 20 Health or 10 Magicka or 10 Stamina.
Therefore, it becomes a no-brainer to put all Attribute points into Health once you hit level 50.
Of course, BEFORE level 50, you are probably better off increasing Magicka or Stamina or having some balance of stats. This is because you are highly unlikely to Overcharge any resource stat while levelling unless you only ever put points into it.
(*) Having a lot of Health on gear risks either trivializing content by creating uber tanks or uniform high survival builds in endgame PvP (effectively turning endgame players into powerful NPCs).