Cultivation isn't really what I feel the right perspective to take as much as it is practice with a goal in mind. Cultivation is not as specific and can mean many things that can complicate what the correct meaning and application is. Therefore, I prefer the term and perspective of practice. That falls in line with every thing we do.
Just in aikido alone, you have Ueshiba point blank demonstrating Funakogi Undo with Terry Dobson and talking about how you need to cultivate the body. That's only one nod to many, many Asian texts where people "in the know" gave a nod by relating the root strength of martial arts to one's internal conditioning and prowess via the idea of "cultivation" and adhering to the laws/connections between heaven and earth.
The notion that internal strength just "happens" because it's in nature is only espoused by those that don't actually have any abilities in this area. Internal power in the martial arts landscape references very specific things around manners in which the body is conditioned through physical training of the bones, connective tissues, etc. through poses, postures, gravity drills, breath drills, etc. .. different styles have (or had) different means and emphasis on aspects of this but they all related towards the same fundamental weird and different types of strength that martial arts training was supposed to confer.