If we were talking about a game like DOOM, which was 1080p 60fps on PS4 and on Switch it's 720/576p at 30fps and also lost a lot of visual detail, I would agree with you: the Switch version should score less. Because the difference is big enough to make a relatively negative impact on both graphics and gameplay (although I must say DOOM is one of the best games the Switch can offer, third party or not, even at 30fps)
But DQXI? The game was 900p 30fps on PS4. On Switch it moves between 900p and 720p at the same framerate. Sure, it has some more pop in and texture detail is slightly reduced... but in general, the technical differences between Switch and PS4 are some of the smallest we have seen in an AAA current gen game ported to the Switch. It's so small that if I show you random screenshots of the Switch version many of you will probably say it's the PS4 one.
So, in a visual and technical level, DQXI on Switch can stand on his own as one of the prettiest games on the system. Add to that all the extra content in the form of 2D Mode, new story arcs for each character, more mounts, an orchestrated soundtrack and many other QoL improvements like speeding up battles... and you have definetly a much better game than PS4 and PC. And as such, it should score higher.
