With more focus on HTHS the analogy only becomes: ripping the carb off your supercharged 383 and putting on new-old-stock of similar appearance and slightly more cfm, then enlarging main jetting and loosening an idle screw and calling it good. Which can work for 30 minutes or 30 years, but no, it ain't necessarily so.
The Mobil1 ESP x2 0W-20 for example appears to be thicker (depending on perspective) than the two 5W-20 oils mentioned last. HTHS values are virtually indistinguishable here and for certain areas or higher shear rates the behaviour is different again. xW-30 up to 3.2 in HTHS would be a reasonable alternative when questioning 0W-20 in summer heat.