I believe manufacturers were forced to limit 1080p output to HDMI.
This is correct regarding Blu-Ray players for the 1080p/24fps native content of a Blu-Ray disc. But this is not a requirement for a DVD player that scales the DVD's 480i native resolution to anything else, including 1080p/24fps or 1080p/60fps . . . as the player isn't actually letting any native HD content "out of the box".
But if you think of it another way, the content on the DVD is always 480i, and the end form is the multiplexed parallel output from the digital processing engine inside your monitor . . . before it's actually sent to the LCD or plasma panel (or whatever). So your end picture quality is always dependent on the performance of every conversion or scaling step the information goes through, and how they all interact with each other . . .
. . . so setting your player to "1080p" output (from DVDs) doesn't necessarily always give you the best picture.
