They’re even less than 1080p? Wow. I wonder if Lucas has regrets about shooting them that way now.
They are 1080p, and were shot in full 1080p, but most AOTC scenes were compressed with 3:1:1 subsampling (i.e. true resolution of 1440x1080 for chroma and for 960x540 luma) as that was the limitation of the HDCAM tapes. It was not shot using an anamorphic lens, therefore it was cropped from 1080 to 817 vertical lines. For the most part the result looked great (even on IMAX), however the low chroma resolution posed problems for compositing, and those are definitely visible in the end result. But they didn’t always use HDCAM for storage, so some scenes were shot and stored at full 1080p with 4:2:2 subsampling. IIRC the cameras were much larger and more cumbersome when compared with 35mm cameras, so they had a lot of disadvantages, beyond the relatively low resolution of the HDCAM tape storage.
RoTS was shot and stored at full 1080p with 4:4:4 subsampling, also it was not shot using an anamorphic lens, and therefore was cropped to 817 pixels as well. So it’s true that AOTC is mostly below full 1080p resolution (for the live-action stuff), but most/all of ROTS is full 1080p for all live action (minus any occasional scene that was shot early or borrowed from leftover AOTC material).