In which country are you? Have you heard that from your teacher? In my music encyclopedias, pianos and percussion instruments are always different categories,

In which country are you? Have you heard that from your teacher? In my music encyclopedias, pianos and percussion instruments are always different categories, or see e.g. here: https://www.britannica.com/art/piano https://www.britannica.com/art/piano https://www.britannica.com/art/percussion-instrument https://www.britannica.com/art/percussion-instrument But of course it's just language, which is "the source of all misunderstandings", as they say. The physical modeling is a bit more complicated than you envisioned; e.g. https://www.modartt.com https://www.modartt.com, which is a great simulation, even has different physical models for different piano brands, taking into account the specific differences in materials and construction methods.