“But we are never given a reason why H13 is good enough, but E12 isn’t.”
Wirecutter dismissed IKEA’s cheap purifier for not being “true-HEPA,” a term with no legal or scientific meaning. The IKEA filter is an E12, one class below the H13 Wirecutter wants. The purifier it recommends instead happens to pay affiliate commissions. A review site that earns on the alternative is not a neutral judge of the cheaper one.