They weren't. Experiment One, Thrull Parasite and Wasteland Viper don't make any sense in the other color.
You could just as easily say Judge's Familiar doesn't make sense in White... in fact even moreso than any of those four, which all have a guild mechanic common to other creatures of the guild of both colors. White only got the Force Spike effect in Planar Chaos.
It isn't like Flying is a predominantly white ability either. I'm pretty sure it's tertiary in white, with blue being primary and red having secondary. But flying is common enough overall that it's hardly noticable, and entirely negligable. Thrull Parasite definitely could have worked in white, and Experiment One could have been five colors and it would hace made sense. Do you see that thing?
Flying is much more common in white than red. For example, M13 has 7 white flyers, 7 blue, 5 red, 5 black, 0 green. Plus one white card gives flying to creatures (Ajani) and one blue makes flying tokens.
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I was under the impression that flying is primarily white and secondarily blue, the reason being that cheap fliers fit white more because it is the color of efficient weenies whereas green is the color of efficient fatties. White also generally gets better fliers than blue, as is the case with Serra Angel and Air Elemental . Blue does occasionally get lucky with cards like Zephyr Sprite and Judge's Familiar , but it's not supposed to have creatures as efficient as green or white, or indeed even black or red. Blue is supposed to have the least efficient creatures, at least where attacking is concerned.