Ok, that makes sense. With NTSC-PAR, aspect should look about right with OSSC in DTV-480p mode but I’ll burn 240p suite soon myself and test it out. 1:1 VGA-PAR on the other hand, is optimal for CRT monitors (like one in the linked pictures) which have size adjustments so that one can fit 640×480 (?) area perfectly on the screen regardless of blanking lengths. In digital domain, the same effect could be achieved with active area adjustment.
After I finish advanced timing editor feature for OSSC, one can just set active area to 640 instead of 720 in DTV-480p mode, which then shows VGA-PAR correct while still using optimal sampling rate. However, some TVs may not accept the tweaked mode.
I wonder which PAR game developers did usually use. As development was done on PCs where assets most likely were viewed at 1:1, did they take into account that they will end up thinner on a CRT TV?