Is Apple allowed to distribute GPLv3-licensed software through its iOS App Store?

I have no intention of trying to argue with rms about this (or any other GPL-related) issue. But I think there's an interesting difference between GPLv2 and GPLv3 that gives rise to a new line of approach to the issue.

The previous issue with Apple was, as the OP notes, GPLv2-specific. GPLv2's handling of additional obligations being placed on distribution is to shut down the right to redistribute, in s7:

If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all.

Which led to the suggestion that Apple had no right to distribute GPLv2 software, and the discussions that arose and are documented in the question, supra. GPLv3 takes a more interesting line, in s7:

If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term.

When GPLv3 software is uploaded to the Apple store, that conveyance is covered by GPLv3. Apple's standard restrictions are placed on it afterwards; thus the recipient, by GPLv3 s7, may simply ignore them. An exception may arise when the software is uploaded to Apple by a rightsholder; then an argument can be made that the rightsholder, knowing that Apple will place these conditions on redistribution, has consented to them. But as long as the upload is done by someone who isn't the rightsholder, and who has no power to consent to additional terms, then the GPL, coming first, takes precedence.

If Apple chooses to redistribute software conveyed to them under the terms of GPLv3 (and I firmly believe that Apple is doing the distribution here, and that arguments of "mere conduit" protection do not apply) then they have consented to the GPL, and their terms, to the extent that they are incompatible with GPLv3, are thus invalidated by GPLv3 s7.