It's less about coachability and more about "bendability"- are they open to test their thinking and approach when presented with data, anecdotes, and the perspectives of others? Ultimately, strong leaders have vision and are steadfast in their decision making but seek the input of others. Part of this is being a good listener, making others feel heard, and having a self awareness of where one's own understanding is limited. This may not mean that a founder takes and does everything suggested at face value, but can incorporate them in their decision making and in the event they disregard something, can share why.
Prior
Coachability is an important founder quality. A founder who will take to coaching has a higher likelihood of success because they will take instruction.