This is still a bug.
I was dealt the 5d, 6d. I have been trying for a straight flush and was well over everyone at the table.
I believe Max bet ~5.5k preflop and Tycho called.
As you can see, flop was 2d, 3d, Th.
Max went all in. Tycho called with just change.
As I was ~5% to get the straight flush, I called.
Turn was Qh and river was 4d.
Max was holding Tc, Jc.
Tycho was holding Qc, Ad.
As you can see, for whatever reason, it says "Flush" and the straight flush cards are counting down. (Could this be part of the problem?)
While I still had the best hand and won, I did not get awarded the correct winning hand (e.g Flush instead of Straight Flush) and thus no Steam achievement credited (I did verify I was connected to Steam at the time as my friends list was visible).