The only truly low ETM cartridge that I am aware of new today is the Dynavector Karat... (which is an MC cartridge, but with a cantilever of under 3mm length) - at a guess, without measurements and calculations... but based on knowing the resonant frequency is around 50kHz, an ETM of around 0.1mgI see EPC100mk4 mentioned anytime someone brings effective tip mass in MC/MM. But because something was achieved once upon a time doesn't mean it is true for cartridges available on the market. I don't think absolute ranking of all times is relevant here, however, what is relevant is what you can buy and put on your turntable.
Do we have any reliable ETM data for currently produced cartridges, not something made 30-50 years ago? Otherwise we can neither dispel nor confirm "the myth"
The other low but not VERY low ETM cartridges that I know of are the soundsmith MM (MI actually) - at 0.3mg they are low, but nothing like the Shure V15VMR which achieved 0.175mg, or the EPC100mk4 which achieved 0.055mg
Roughly speaking, current top flight cantilevers are around 0.3mg
Which is sad really.