TL;DR: Homeworlds should be exempt from having 'Planetfall' bonuses. ("The reported location of the first scouts to set foot on this world")
Reason: That species didn't land on and colonize that planet, at least in any way relevant to the game or bonus. They've just always been there.
Note 1: In the name of balance, you could just change the description to something more relevant to a homeworld, EX: Site of first space launch.
Note 2: Ice meteor with microbial life form thing doesn't count as planetfall, cause we couldn't exactly send scouts out of the meteor.
Note 3: My Earth's planetfall was in Sub-Saharan Africa, pretty ironic given humanity's origins 