You raise an interesting point, but I'm trying to visualize an alternative. Just trying to understand what you mean, not being snarky. What orientation would be an improvement?
Are you saying that instead of a straight up/down fin orientation, it'd be better to angle the fins away from the heatsink's midline to direct airflow - like oriented downward but slightly angled by say bending or curving the bottom of fins 30 degrees outward?
Most modern ITX boards have large rear IO housings/VRM heatsinks immediately to the left, and two RAM slots immediately to the right of the CPU socket, which in the case of the L9a due to it's slightly rectangular shape and non-flexible mounting orientation means that the entire exhaust is forced to find less ideal routes to escape.
Noctua (and other manufacturers offering similar design), need to either keep all ITX offerings strictly square and compatible in any orientation, or at minimum, direct the fin stack in a way that is actually conducive to the vast majority of ITX builds.
Picture below isn't a Noctua L9i/L9a, but is a Cryorig C7 G which also suffers from the same issue. They offer mounting clips for alternate fan cooling as implemented here (Noctua NF-A9x14 fan) but their fan clips are only usable in one orientation, forcing poor @GuilleAcoustic
to suffocate his exhaust in the same manner since the clips simply do not fit with the cooler rotated 90 degrees.