When a logistic group gets set for a spaceship it sets the pickup to be the default location. I.E. Stack Inserters are requested from Gleba. There's no way to change this though, because if you update it, the update gets immediately overwritten by the logistic group combinator. Not sure if there's anything that can be done, but if there was it would make setting up my on demand spaceship cargo hauler a lot simpler.

If you used Planet Request Group, including the desired import location (eg. [planet=vulcanus]) in the logistic group name should solve that issue - as soon as a platform arrives in orbit around the mentioned planet, a temporary request group is added for that platform that has the correct items/amounts/import location set. The only issue would be that the request with the default import location for that item would be active as well, though you might be able to do some circuit magic to just empty the group whenever the platform is above that specific planet - or maybe just set a large negative request for that item from that planet in a static logistic group?