They changed the definition of a "brilliant" move several years ago. Basically, any sacrifice that is a best move or near best is called brilliant.
From the Help pages:
Brilliant Moves are always the best or nearly best move in the position, but they are also special in some way.
We replaced the old Brilliant algorithm with a simpler definition: a Brilliant move is when you find a good piece sacrifice.
There are additional conditions:
You should not be in a bad position after a Brilliant move
You should not be completely winning even if you hadn't found the move.
We are also more generous in defining a piece sacrifice for newer players compared to those who are higher-rated.
In this game, playing as black, I got multiple brilliant moves from sacrificing the rook and queen, though I missed some checkmate opportunities. The endgame became a race against the clock, and I was trying to win on time by just making moves as fast as possible, which I definitely could have pulled off, but my brain basically switched to autopilot and didn't realize I was repeating the position until it was too late. I think this is the dumbest way I've missed a win.