... and even if you deliver 100% of your 175% commitment, I have a somewhat dark and cynical hypothesis that the manager may secretly feel guilty about overwork

... and even if you deliver 100% of your 175% commitment, I have a somewhat dark and cynical hypothesis that the manager may secretly feel guilty about overworking you and resolve this guilt by downplaying your achievements. Merely feeling or behaving like a doormat for no reason will make many people around uneasy. Any situation that shows you somehow deserve it, relieves them. If they aren't self-aware enough to recognize this, congratulations, you are training them to exploit you.