On Chess.com, a brilliant move isn't always the best possible move. It is about 95% of the time, but not always. In fact, I think I've had 2 or 3 brilliants (including my very first one) where there was a "better" move on the board.
Now, back to the point. I think the reason for the situation here is that Rd6 is obviously winning (it's essentially an equal trade of pieces, due to deflection, and makes a pawn promotion unstoppable), while h6 seems like a huge blunder until you look more closely.
Can anyone explain why h6 in the position is rated as a brilliant move though Rd6 was clearly better thanks to mate in 6? As I suppose a brilliant move gotta be not only tricky but also the best move in a specific position.
Thanks
I'm actually looking forward to the answer to understand more deeply how a brilliant move can be made to get more in my real games