That is correct; and legacy DVD's are actually encoded in only 480i, so "progressive scan" players are already upconverting (deinterlacing) to generate the 480p output.
Just a FYI,
DVDs are encoded by "field" rather than by "frame", so in one sense progressive-scan DVD players do need to do a little bit of work to recombine the proper pair of fields back into a complete frames. And there are different ways of doing this (reading flags to instruct you as to which fields go together, or analyzing a series of fields to determine the cadence). But when done properly, you get back the *real* actual original progressive frame that is identical to the frame before it was split into fields.
This is only true of native "frame" based video images like those derived from film. Native 480i signals, like from standard-def video cameras, are inherently 480i because there are no "pairs" of fields that make up a compete frame... each field was recorded 1-60th of a second apart from the one that came before. So when you "deinterlace" raw interlaced video material, you *are* indeed interpolating to fill in the missing lines.
But when you deinterlace native progressive material, even when it's been split into fields as is the case on DVD, you don't interpolate at all... you recombine and get back the frame you started with.