The fact is that it's his creator's statement that he is eight inches tall, though.
Many of the graphical items listed in the linked post all have technical explanations mainly relating to the "ten foot user interface" - i.e., it's about clarity from a distantly-viewed display. You can also validly bring up the technology left behind by the ancients as a possible in-universe explanation, as well.
Shiver Star is unlikely to be Earth, as the series has often made references to contemporary technologies from Earth that match the release-times of the games; One of the oldest ones (if not the first one) was the Computer Virus/Battle Windows boss in Kirby Super Deluxe, which in its original, non-remake incarnation was a direct rip of the look of the Mac OS of the time, and I believe the most recent one was Daroach making a reference to the Nintendo 3DS a few years ago. If Earth's gone, those guys can't possibly know about those things.
(EDIT: And there's also the fact that Popstar/Gamble Galaxy is located at the other end of the Milky Way from us, if I'm remembering rightly.)
There's also the fact that, at twice Kirby's height, Dedede's height
exactly matches that of the Earth penguins that he is closest to, as well (these being the Little Blue Penguins, hailing from Australia and New Zealand - he even has a filter applied to his Smash 3DS/Wii U voice-clips to make him sound more like them). This is a whole other matter in and of itself (I'll keep it short), but the fact is that Dedede is undisputably intended to be this way, making his height a bit of a lynchpin here; His hooked beak, forward-leaning run, and complete lack of facial markings are other traits completely unique to this species that he shares with them, along with his height. The amount of detail Sakurai (who seems to have shown a bit of favouritism toward him at times, and who appears to know a fair bit about Blue Penguins) put into Dedede is quite high, which is why this particular height is important to note. After all, Sakurai officially said that Kirby is eight inches tall, and it follows that he happens to be half the height of the one recurring character who is modelled on an animal species found on Earth.