Stuffing emotions

A friend of mine has done TSG with her family over the years. She cautioned me as I was starting the program that while it was great, she found that the focus on calmness made her kids believe that no emotions except happy are ok, and that it’s not ok to feel other emotions like frustration or sadness or anger, etc. she said it was kind of damaging for one of her kids in particular.
I would love to know your thoughts on this, and how you would recommend implementing the program while also not teaching kids to stuff or bury their emotions. Have you ever had any experiences with this?