It may be hard to turn up anything about this question. The serious problemists are only looking for positions with unique solutions. The current best result (with no special conditions) seems to be Labelle's 19.5 move game. Labelle only tested about half of all possible final king positions, so there's still the possibility of a future improvement.
There is a considerable history among problem composers about attempts to find a shortest proof game for positions with only two kings remaining [...] There have been some unique 16.5 move solutions found under the condition that the FIDE Dead Reckoning rule be suspended. [...] To my knowledge, the best unique solution with no special conditions is a 19.5 move proof game composed by F. Labelle in 2012.
The 19.5 move position is the only 2-king proof game known. Dead Reckoning has made no difference to this search. There are some other boards with just a handful of pieces left. A few are broken by DR, others are only rendered sound only because of DR, most seem to be independent of it. As far as I know, there was still some search space unexplored by Francois Labelle when he announced his result, and I am sure he will continue looking.
Since we have a unique 19.5 move solution, and a non-unique 16.5 move solution, any new results about a 30 move solution would not seem to be of much interest.
By the way, abivasu's game is not a valid solution unless the caption "No Dead Reckoning" is included. Without that condition, the game ends in a draw after Black's move 28, with a knight still on the board.
im sorry, i said move when i meant ply...what i meant was how many 16.5 solutions there are.