Epiphytic orchids use the pot and substrate primarily for mechanical stability. In the wild, their roots spread far and wide on the bark, so there is no drive to stop growth if in a small pot. If the aerial roots are unable to find additional solid matter to adhere to, it
may, slow the plant’s growth a bit, but that’s about it.
The materials you referred to sound like coconut husk chips (but could also be bark - a photo would help), and the white stuff is probably perlite, sometimes called “sponge rock”, which is also of volcanic origin.
As far as the question about changing it, there are two things to consider, and the first and most-important is “does that potting medium work well with your specific cultural conditions and watering abilities to give the plant what it needs?”. If it does, there is no need to change. If it doesn’t, you must contend with transitioning the plant to a new root system. Rather than adding to a long post, please read this:
preventing repotting woes