Thanks for checking that out, Brad!
My concern wasn't that someone was being deceitful. Rather, I thought that maybe it recorded in 16-bit and then someone simply chose "Save as" and selected 24-bit. As you point out, though, that would just lead to having padded zeros.
I agree, there's no reason do doubt.
Am I right that this is the highest digital quality U2 release to date? (The previous, I believe, was Achtung Baby on hdtracks.com in 44100 Hz / 24-bit.)