EDIT: corrected info about TV AR settings.
I’m not sure either. On the VT60, Lx3 modes require the TV to be in 16:9 mode and Lx4 requires 4:3.
For OSSC optim modes, adjustments to H.samplerate are always necessary to restore horizontal scale and remove the blurred graphics.
With generic 4:3 modes, the horizontal scale is accurate on the default settings. Some consoles may require tweaks to backporch. All consoles require V.active 256 >> 240 reduction in order that restore AR.
I’ll take some pics tonight and maybe someone will be able to figure it out. My guess is that it’s due to the TV’s processing of the signal data.
Congrats on the discovery re H.samplerate. I was tweaking some stuff yesterday, hoping to make some sort of discovery. Based on what you’ve found, I’m going to note down the various tweaker settings for each console and linemulti mode and see if there is not some similar relationship that will work for the VT60.