I think your question is ambiguous or meaningless, as the answer is both Yes and No. The use of gapless in "mode 2" implies support for the SetNextAVTransportURI protocol. Let's break the question down a bit:
Does MC support gapless via DLNA push? Yes.
Will gapless via DLNA push work with hardware that doesn't support gapless via DLNA push? No.
Does that make it clearer? MC's ability to support gapless isn't affected by the renderer's ability to do it.
Does MC support sending MP3 to any hardware? Yes.
Will any/all hardware play MP3? Not necessarily.
Does my PC support a HDMI/DVI connection to a TV? Yes.
Will it work with a TV that doesn't have HDMI/DVI? No.
Do I have the ability to speak Welsh to any person on the planet? Yes.
Will I make myself understood if the other person doesn't understand Welsh? No.
My actual question is: Does MC Support gapless, DLNA playback from MC ("Play to"/Mode2) function for ANY hardware on planet earth (e.g. Piccolo, Linn)?
You don't need to know a thing about SetNextAVTransporURI action to answer the real question.
You do, because gapless DLNA playback requires SetNextAVTransportURI. MC does it, but not all renderers do it. MC either supports DLNA protocol or it doesn't. It does do it, unconditionally, regardess of the renderer. It doesn't drop support for the protocol if the renderer doesn't support it.
You can hop a plane and come to my house and listen to the DNP-720AE play gapless in Mode 1 anytime.
I don't think anyone is disputing that, it's stated in the FAQs that you are suspicious of, and you want people to believe you when you prove that the FAQ was correct even though you're suspicious of it! It's also stated that the 720AE does not support Mode 2. And MC does support it. It just aint gonna work. You need a device that supports gapless via DLNA push, MC's support for the protocol is not in question.
You own a Piccolo. What happens when you "play to" Gapless flac files by way of DNLA FROM MC? 6 sec Gap added or not?
I think he's already answered this: " I have since tested this many times and am truly enjoying gapless playback on my live albums. I have even bought an additional Denon CEOL Piccolo device for my office."