Of course it's not 4.6-120mm. 26-678mm is the 35mm equivalent focal length for that. That takes into account sensor size. Your camera has a small image sensor, hence it has such a focal length range.
No 35mm lens will ever span 26-678mm, that's insane. You'd have to use several separate lenses - e.g 24-70, 70-300, then a x2 adapter for that (only prime lenses are longer than 300mm), and it'd still be a bit short.
Slightly off-topic-but-also-related: While accuracy-checking my knowledge of lenses, I came across the longest lens ever made by Canon: the
EF 1200mm f/5.6 USM. Discontinued now, it was only manufactured on order, with an annual production volume of 2 lenses. It only cost
89,579 USD. Being discontinued, of course, being such a rare item, it now costs nearly twice that. Look at that baby:
I'm only $119,995 short. Anyone willing to spend a few bucks for my birthday?