For the first part, maybe it only showed part of the follow-up which involved sacrificing, and for the second part the "better move" likely hung the piece for a good reason. Remember, Stockfish is the most advanced chess bot in the world, so it will see things far ahead in complicated sequences "invisible" to the human eye.
About the feedback after a game seemingly giving bad advice
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After I play a game, I will go to the press 'feedback,' and the advice seems not to make sense or contradict itself. It will say something like 'you had a chance to win material,' so I go back and press 'follow up,' and it shows me losing material in the follow-up. Or it will show a "better move," but the move will leave an essential piece of mine wide open. Have other people noticed this?