The prohibition is narrower than "no dollar limits", and the qualifier is the whole story. What 147.126 bans is a dollar limit on essential health benefits, the benefit categories defined by section 1302(b) of the Affordable Care Act. The regulation then says expressly that its rules "do not prevent" a plan or issuer "from placing annual or lifetime dollar limits with respect to any individual on specific covered benefits that are not essential health benefits to the extent that such limits are otherwise permitted under applicable Federal or State law". That sentence is why dollar-capped designs did not vanish from the market. It is also why the practical question about any capped product is not "is this allowed?" but "what is it capping, and does the law count that as an essential health benefit?"
A second construction rule catches a design people expect to be prohibited. Under 147.126(b)(2), the rules "do not prevent" a plan or issuer "from excluding all benefits for a condition. However, if any benefits are provided for a condition, then the requirements of this section apply." So a total exclusion is treated differently from a capped benefit, and other federal or state law may separately require the benefit anyway. A third exception is narrow and technical: a health flexible spending arrangement offered through a cafeteria plan is not subject to the annual-limit rule at all.
Three legally distinct escape routes exist, and collapsing them is the commonest error in this subject. They are not variations on a theme; they work by different mechanisms and carry different consequences.
The first is excepted benefits, and it is statutory before it is regulatory: 42 U.S.C. 300gg-21 provides that the requirements in which section 2711 sits "shall not apply to any individual coverage or any group health plan (or group health insurance coverage) in relation to its provision of excepted benefits", with the qualifying benefits defined at 42 U.S.C. 300gg-91(c) and several of them subject to conditions. The individual-market list is 45 CFR 148.220, which states that "[t]he requirements of this part and part 147 of this subchapter do not apply to any individual coverage in relation to its provision of" the listed benefits; the parallel list for group health plans is 45 CFR 146.145(b), which is the relevant one for a plan offered through an employer. Accident-only coverage, disability income, and several others are excepted in all circumstances. Limited-scope dental and vision, long-term care, specified disease or illness coverage, and hospital or other fixed indemnity insurance are excepted only when provided under a separate policy and, for some of them, only if further conditions are met, such as the fixed indemnity requirement that benefits be paid in a fixed dollar amount per period or per service "regardless of the amount of expenses incurred". A product on this list can cap in dollars because part 147 never reaches it.
The second is short-term, limited-duration insurance, and it escapes by an entirely different door. 45 CFR 144.103 defines individual health insurance coverage as coverage offered to individuals in the individual market "but does not include short-term, limited-duration insurance". The rule in 147.126 applies to issuers "offering group or individual health insurance coverage", so a policy that is not individual health insurance coverage is outside it. Nothing about that turns on the benefits being limited in scope.
The third is coverage that is not insurance at all, such as a health care sharing ministry, where no issuer and no insurance regulation is involved in the first place.
The history explains the name, and it should be read as history. HHS regulations issued in 2010 phased the annual-limit ban in rather than imposing it at once: plan years starting between September 23, 2010 and September 22, 2011 could not limit annual coverage of essential benefits below $750,000, and the restricted annual limit rose to $1.25 million and then $2 million before all annual dollar limits on essential health benefits were prohibited for plans issued or renewed beginning January 1, 2014. During that window HHS could grant temporary waivers where compliance "would result in a significant decrease in access to benefits or a significant increase in premiums", and mini-med plans were the reason the waiver process existed. Applications closed on September 22, 2011, and CMS states that "after 2014, no waivers of the annual limit provision are allowed." The restricted-limit and waiver paragraphs no longer appear in the current text of 147.126.
One caution about sources here. The CMS page carrying that history is written in the present tense of 2011 and says "Starting in 2014, the Affordable Care Act bans annual dollar limits", which was accurate when written. It is evidence of what happened, not of what a plan may do today; the current regulation is.