What proposal are you talking about? The one which proposes to shrink blocks to ~300kB or to keep them at 1MB for 7 years?
Yes, that one. It does more than that as it actually grows on a fixed schedule.
OK, I understand, core devs are numerous. It's nearly impossible even to gather all of them in one meeing. So how one could negotiate with them? Saying that they were not represented at the meeting is an excuse for doing nothing. I'd say that there were enough influential, prominent devs there to properly represent their party and make the agreement meaningful.
No. The Core devs at that meeting did not represent Core. As I understand it, they made it very clear at the meeting that they only represent themselves as contributors, not representatives of the project itself. Furthermore the only statement binding them to do something hard fork related is
The Bitcoin Core contributors present at the Bitcoin Roundtable will have an implementation of such a hard-fork available as a recommendation to Bitcoin Core within three months after the release of SegWit.
Notice how it does not say that the Bitcoin Core project will adopt said proposal, only that the contributors present will make such a proposal which they can recommend to Core.
But currently he's apparently the only one among segwit supporters who tries to resolve the conflict in conformity with the agreement.
His proposal is not in conformity with the agreement. It came way past the deadline (luke-jr's came before the 3 month deadline), he was not at the meeting so his proposal does not count, and his proposal is not recommended by the Bitcoin Core contributors present at the meeting.
Anyways, the Hong Kong agreement is really not in effect and not binding anyways so this is pointless to argue. Technically all parties upheld their parts of the agreement due to the vagueness and loose wording of it.