Xcode 4.2 was also only available to iOS developers.
Xcode 4.1 was part of the Lion pre-release, so I don't think that iOS developers got it during beta, though apparently it was made available for SL users a few weeks after Lion shipped.
It at least makes sense to limit the betas to the Mac program only if the tool in question only works on a prerelease OS (I assume that's the case with 4.4 and ML). But limiting it to iOS developers only makes no technical sense at all.
Edit: 4.4 works on 10.7.3+, so yeah, this is just the usual bullshit.