Why isn't this Insufficient Material?

https://www.chess.com/live/game/2449103502

The final position looked like this:

And white ran out of time. Even though it is physically impossible for black to checkmate with the pieces he has, chess.com still gave black the win.  Why?

did black promote to a same-colored bishop instead of getting a queen? Why? You see a proper compliment of bishops (1x white 1x black) is sufficient material to mate in a corner. But you are correct that two black squared bishops and a king cannot mate.

I wanted to practice my 2 bishops vs king checkmate, but forgot I couldn't do it if they were on the same color!

Anyways, I think this is a bug, correct? Chess.com should correct this in the future to be a draw. 

You are right, it is insufficient material. But I have a question. Your blitz rating is pretty good and your tactics rating is fair, so why would you need to practice a two bishop checkmate? I dont remember what rating I was when I learned that but at 1500 isn't it automatic?

Because programmers are good at programming, and shyt at chess.

And businessmen like Erik are good at making money, and shyt at chess.

Enough said.

Now this is really weird. At least you have discovered that Chess.com rules this endgame as a win for the player having two bishops residing on the same coloured squares.

Precisely because fryedk rating is good enough, he/she wants to explore new or uncommon things in the chess. Or perhaps fryedk has not held sufficient experience with the king and two different colour squared bishops versus bare king endgame even though his/her rating is high enough to suggest good endgame handling skills.

I myself have not actually encountered these endgames that often yet, so I have very little practice on these endgames.

Inadvertent programming error likely, algorithm written as 2 bishops = win, when should be 2 different colored bishops (i.e. light and dark squared) = win.

Quite likely. The programmers may have indeliberately omitted this exclusion. Otherwise, the game would be an immediate board from the time only those four pieces are on the board (for example, due to a White piece being captured by a Black piece, a Black piece being captured by the White king or the final move being a pawn promotion to a same colour-squared bishop).

Chess.com's criteria for insufficient material is very simple (A list of three or four material combinations).   I doubt that anyone thought about two same-colored bishops because that situation is highly unlikely.  Now that we're aware of it, Is it worth the effort to add programming for a situation that will  rarely, if ever, occur? 

Note:  I checked an old version of the USCF rules (I imagine the latest rule book is the same).  Guess what?  Drawn game is lone K, K+N, K+B, K+2N.  No mention of K+ 2 same-colored bishops.  FIDE avoids this by requiring checkmate by any series of legal moves.

Even USCF rules also do not include it??? Weird.

I have already considered the possibility of the same colour-squared bishops case, but have always assumed that it is an instant draw due to the lack of insufficient material. Well, that is until half an hour ago when I saw this post.

 What's interesting is that USCF has two rules, insufficient material to continue, and insufficient material to win on time.  The former has a provision about legal moves leading to checkmate, the latter does not.  Looks like an oversight by USCF.  Again, I'm looking at the 5th Edition, things may have changed in the 6th Edition.

Wouldn' t work, mate is possible here:

The final position in the game included two bishops residing in the same coloured squares. Apparently the Chess.com system does not distinguish this king and two same colour-squared bishops versus bare king endgame from an ordinary king, light-squared bishop and dark-squared bishop against lone king endgame with respect to the outcome when the side having the bare king loses on time.

If black has a bishop of a different color mate is possible. But if white has 2 bishops of same color, and black has no other pieces or only has bishops of the same color as the white bishops, mate is not possible. 

@ fryedk, thanks for showing the possible mate position. I think it is playable in real life but with conditions.  You are white but you will move the black pieces, your opponent of course is black but will move your pieces... what do you think? 

this is bacicly a biship and king versous a king