I think it may help a little. Looks like the distance between the lenses and the mouth (nose area) is a bit too long and repainting the mouth would only make a small difference in the right direction. For myself the part below the mouth on the ANH version was too long and nose area too short. They made that smaller (better) on this version but then elongated the nose area
Yeah I think they "reversed the wrongness" on this release - the ANH version has that underbite/bull-dog look because of the too-big chin area and the too-short nose/bridge area as you mention, and this ROTJ version does seem to have the "off proportions" now reversed: chin area (slightly) too small and nose/bridge area too long/big.
So even though over-painting the mouth will slightly reduce the nose area, there's still that too-small chin area that throws it off.
Stock I do prefer this new version though - it really does looks decent. The ANh helmet felt a lot wrong to me, despite the amazing apps and ultra-clean sculpt detail. Other than that custom stunt sculpt, I still think the Marmit sandie helmet has the most accurate sculpt of all - it resembles the ANH hero quite a bit. The issue with the Marmit helmet is that its a fairly soft vinyl sculpt so just doesn't have the crispness of these newer versions and it has to be painted.