Wow, that teacher needs a teacher of his/her own! I can't believe this. The only time you'd say that if one wants to become a CONCERT pianist. To achieve that level of performance, you might as well start practicing in the womb! That's a whole different category. You have to be ridiculously good by the age of 15 to even have a chance. Even then you might not be able to make it.

Obviously the older you get, life gets in the way and it becomes harder and harder to have a set practice schedule, but there's millions of determined people in the world! I know of many pianists friends who started serious lessons in their 40s. 5 years later, they can play pretty advanced stuff on a legit acoustic piano!

When it comes to any form of musicianship, age means absolutely nothing, unless that person used it to develop real skills.
Many have no idea how music works and yet they manage to have strong opinions about how things should be done.

With that mindset not even a Sonata would be created by now.