Indeed, my Philips TV does not change aspect due to H.Active at all, although it has some limited tolerance to how small/large the H.Active can be (I’m thinking because of limits to the H.Blank in relation to Active). The only way for me to affect aspect is to increase/decrease H.Samplerate.
EDIT: I found an exception to this, which concerns H.Active of 720 vs 640 (with 480 active height), which makes sense for these resolutions. The former will be treated as 480p, the latter VGA, and they are identical unscaled, but different when scaled to fullscreen (due to different pixel aspect ratio). Annoyingly though, my TV does not scale 480p properly, it seems (screen is too narrow).