True - at least most "737-only" low-cost airlines (Southwest, Ryanair, ...) use the older 737 models and the MAX (which Ryanair has rechristened to "737-8200" because of... reasons) interchangeably AFAIK.
According to https://www.faa.gov/sites/faa.gov/files/FSBR_B737_Rev_19_Dra...
> In January 2021, the FSB conducted an analysis of the changes introduced for the 737-8200. The analysis identified that the 737-8200 is functionally equivalent to the 737-8. The 737-8200 is incorporated into the MAX series aircraft group in paragraph 8.1 and in Appendix 2, Master Differences Requirements (MDR) Table.
Both the EASA and the FAA calls it 737-8200. Neither did it to remove the MAX moniker from it.
I booked a flight with them last night, and it’s scheduled to fly on one.