Certainly not trying to create divisions, but if this is just an act of subduing the flesh, as it were, over a practice to help ensure salvation then it’s all good. I just get concened when it may appear to people that they have to do something, or could do something, to earn salvation apart from having faith in what Christ has already done.
You have it right. It isn’t a device by which one gains Salvation, but to grow in holiness.
There is nothing wrong with disciplining the flesh so as to enhance spiritual growth and deny the body, and offering the suffering as part of a prayer for the conversion of sinners. Unfortunately, the secular world will look at it and depict it as some sort of freakish masochism, which it isn’t.