I was on Home Theater Forum when the DVD came out. The original cut was added to the standard DVD release of E.T. at the last minute, in reaction to the fan outcry about being forced to buy the collector’s box set to get the '82 version. In fact, I seem to recall that there was still uncertainty about whether or not the '82 cut was on the regular release, right up until people got copies of it and confirmed themselves that it was included.

If you recall, the release was a fold-out digipak that looked like it should have had an outer slip case but didn’t - I heard at the time that it was because it reflected the disc contents before the original cut was added, and they added the '82 cut to the release so late that they didn’t have any time to print new slip covers. (IIRC, wasn’t there some kind of sticker on the shrink wrap indicating the original version was included?)

I bet the 2005 reissue was just another instance of the studio choosing what they thought would be the most average-consumer-friendly version for the single-disc reissue. (The mid-2000s was a very uneven time for catalog re-releases - this is the same general time frame where Sony was dropping widescreen transfers from reissues of catalog titles like Annie, that had previously been released with both formats.)