Sounds like click bait to me, I haven't clicked it yet.
My understanding of the 401k "true limit" of $54,000 is that the $36,000 matching is per employer. So say you work two high income jobs, or you know your a doctor that has a practice that they are part owner on but also moonlights weekends at big city hospital ER. Your income should be high enough that you would qualify for full contributions at both places for $74,000 in matching, while your personal limit is still $18,000 total. That is still $92,000. If by "everyone can stash $100,000 + into tax advantaged accounts per year they mean "Everyone with two amazing 401k matches, plus a capped IRA, Plus an HSA"... then sure. Even with an IRA that still only $97,500. And since the employer can only match up to your salary of or $54k (the lower number only) You would need access to 2 401ks that would be willing at a minimum to double a $54k salary just to get you those matches.
The solo 401k can only match upto 25% of your salary (in a situation like an S-corp) or 20% of your total income as a sole prop. So S-corp salary would need to be like $145,000 to even hit the $54k limit, or $180,000 in sole proprietor income.