Either it's a common word that is just hard to spell, and sticking to actual spelling is the saving grace as people who didn't know the spell will have a fighting chance to remember it.
Either they come up with an easier to spell version (e.g. "fuxia", but then those who knew the right spell will have to remember both, and those who "misspelled" the flower will be thinking Google's project name is the "correct" spelling.
My conclusion from reading English all my life is that it’s a terrible unintuitive language and using the Latin alphabet for so many different-sounding languages wasn’t such a great idea.
Much like C++; taking the worst of all worlds.
English actually has a set of spelling rules that make it generally possible to predict the pronunciation of most words, while fuchsia is one of the words that sits well outside the spelling rules. The most notorious bits of spelling come when, as here, insistence is made on preserving the spelling despite sound changes making it completely untenable.
The original pronunciation of fuchsia in the German should be something along the lines of "fook-see-a". In English, the 'sia' would naturally want to affricate in that position (the same process that makes -tion pronounced 'shun'), which would lead to "fook-sha". I guess somewhere along the line, the k phoneme dropped, but the u also changes into an English long u (as in, it becomes the 'u' in 'cute' or 'cuticle').
The end result is that to spell the English pronunciation correctly, you need 'f', long 'u', something to spell 'sh' phoneme, vowel to make 'u' long (usually 'e', but 'i' can do the job in a pinch), and then 'a'. 'Fuschia' would be a spelling that comports with the expected pronunciation--while 'sch' is not the most common way of spelling 'sh', it is a way of doing so. And if you have only a vague of memory of what the word should look like, it has all of the requisite letters, and it yields the expected pronunciation--where the 'correct' spelling doesn't.
I'm generally a pretty good speller in English, and I will freely admit that the only way I can remember how to spell fuchsia correctly is that it's the spelling that fucks up--replace k with h.
Google makes a foxy OS. Shame it's not a fire-fuchs
Fuchsia: 39
Fuschia: 19
Fushia: 1
Fuchia: 1
Other: ?
...so we can conclude that the UX of this codename is terrible. Maybe they should change it to something more easy to remember, e.g. Fuxia (Fucksya would probably also be easier to remember, but could be deemed too obscene)?