I can’t answer that. It depends on how they write their recommendations. If they are that tough a grader perhaps they are not naturally inclined to look beyond the facts. I have no idea.
But I do know that we as humans want affirmation from the toughest nuts to crack in life and perhaps that isn’t always the wisest counsel to seek it, in this case from the tough teacher.
Do you know anyone that has asked them in the past. Did they make it into their reach or where they surprised when they had to choose the safety instead because it didn’t work out. Has anyone you know seen one of their recs?
Are you really close with a teacher or your guidance counselor. I would ask them about this and mention your questions. Or instead of putting them on the spot ask them who they would ask if they were you. Maybe they will give you names that indicate what they know about who without having to undermine a colleague. They talk about a lot of things in the teachers lounge.