Well, "epic" is one of those words that is a bit vague in this context. They could just be using the plain-English meaning of epic: someone who can do stuff that's just way out there, in the realms of the miraculous or godlike. Using this, a spell like resurrection is plenty epic, despite being "only" 7th level.
D&D power levels have been divorced from everyday discourse ever since the ELH, and in a sense ever since 3E came out. In 1E through to 3E, by the time you're 9th (character) level you could be pretty epic: you can teleport around the world, raise people from the dead, mow through hordes of mooks, etc. 3E upset things though, by increasing the speed of levelling so that high levels became much more accessible than before; in turn this created the problem of what to do after players had reached those levels. Hence the ELH, and its "more epic than the epic stuff you could do already" vibe. So if 4E can turn the clock back, and reduce power levels at the top end, that would remove some of this dissonance.