I think it's both.
Yes, individual choreographers have quirks and preferences for how they put programs together.
But also, they can only work with what the skater is capable of.
A skater who is good at rockers and counters and choctaws, and with threes and mohawks in both directions, can do a lot more multidirectional skating and complex patterning than a skater who can only look good doing good-direction threes and mohawks.
A skater who can only land their jumps from specific approaches has fewer options than one who is comfortable enough with getting into the jump in multiple different ways.
A skater who is secure over the blades, in the knees and the body core, is better able to use the whole body expressively than one who will lose balance if she challenges herself to use her upper body off axis in creative ways.
And so forth.
Also, a choreographer may ask the skater to do more, and the skater may improve by accepting the challenge, but if it becomes clear that she can't skate a clean program if it is too challenging technically in those ways may need to take out some of the difficult turns or direction changes or body movements in order to get the same jumps landed cleanly and the steps and turns executed cleanly.
(Better to get level 3 on a step sequence without much upper body movement but enough turns and steps for level 4 than to aim for level 4 and not get all the turns counted so you end up with level 1 despite achieving the other features.)
No, I agree with you, if we look at it from skater to skater. For example, if we compare Nathan's Nemesis and Yuzuru's Seimei (or even Wakaba's Skyfall), there's no doubt that Yuzuru's has more complex and multi-dimensional skating, because he is capable of doing more with his blades. What I'm getting at is that from what eppen provided, if we generalize something out from those patterns, Bourne stands out as a choreographer who happens to really include more multi-dimensional skating on her choreography, in general, compared to Wilson or Nichol. Although not as complex as Yuzuru's, Nathan's Nemesis has more multi-dimensional pattern in comparison to his Mao's Last Dancer, and that's why I am more inclined to believe that in this case, it's a particular quirk of Bourne's choreographic style. She can decrease the difficulty of steps and turns, yes, but I think as much as possible, she would still demand her skaters to follow her choreographic pattern.