The level 5 model assumed 3 encounters, with short rests between them. Usong DMG guidelines, it should be 6-8 encounters with 3 rests (1 of them long).
That halves the ROI of rage. Well not quite, as the barbarian uses rage on the tougher encounters.
At higher levels, barb rages approach ecery encounter.
Ignoring action surge is a bit unfair. At least give the fighter a dodge round!
The DMG guidelines also specify that not all encounters need to be combat based, even those that result in monsters showing up. It gives two examples, one with a young dragon that can be solved through stealth or negotiation, and one with a stone giant that will actively shy away from the party.
Additionally, there's not that much room for many tougher encounters, if we follow those same guidelines, which give each adventuring day an exp budget. 4 hard encounters basically almost fully fills the budget at most levels.
I feel like ignoring action surge isn't totally unfair, but it really starts getting into "wait, what are we talking about here?"
The chart was being used for comparing a barbarian against someone who really didn't invest much into defense and compare their tankiness. Now we're starting to get into "If you used literally every possible class feature and item on making yourself tankier, would it be more effective on barbarian or fighter?"
Speaking of which...
An EK spamming shield / absorb elements is a fair comparison with a Totem bear barb spamming rage.
We could get into a whole discussion about it, but even now I'll say EK is an incredibly good fighter class with some shockingly good defense if they try.
But I'm not sure it's a great comparison. That's always the problem with spellcasting vs something more
sustainable. 3 shields a day at level 5 means 3 rounds of protection, and only against either AC-based attacks or one element each round. Meanwhile bear totem gets 30 rounds of protection from almost anything. But that's not really fair to say either, because very few combats go for anywhere near that amount of time.
Getting into items is probably even worse in terms of trying to figure out a fair comparison point. Unless we use AL rules or something.
Honestly though, this whole comparison with AC and damage taken, to me, feels odd. AC is important, but for a barbarian, not as much. This means the opportunity cost of using a two handed weapon is lower, and the payout higher (reckless attack and GWM are a perfect match, but of course it's important to judge when the payout is higher for you then for the enemy). It's more practical to look at a barbarian that only took defensive things in their build when they didn't come at the cost of offensive choices (except maybe for the subclass, probably no need for further complications), and see how that holds up against a similar fighter. And maybe against a more defensive fighter, while seeing what kind of offense is lost.