Adjustments, consent and who is qualified
A hands-on correction is a physical intervention.
Physical adjustment by a teacher is common practice and it means somebody applying force to another person's body, often while that person cannot see them and is in a vulnerable position. Whether the teacher has the training to judge that is not visible to the student.
Consent practice has improved and remains uneven. A consent card, or asking at the start, is now common in better studios and by no means universal. A student is entitled to decline adjustment entirely and should not have to justify it.
Deep adjustments that push a student further into a position are the ones associated with injury, particularly in forward folds and hip openers. A correction that changes the shape of a position is different from one that increases its depth, and the second carries the risk.
Anybody with an existing injury or condition should say so before class and should decline hands-on adjustment. A teacher who responds poorly to that has answered a useful question about the class.
The other thing to say about adjustments is that a good one is usually verbal. A teacher who can say what to change, precisely, is doing something the student can repeat unsupervised, which a hands-on adjustment does not teach. The physical version should be the exception rather than the default.