It's not rare at all in my experience. You just have to have a combination of skills that pays more than average on the open market (big data runtimes or distributed systems, say, or AI, in addition to other domain expertise perhaps), and you'll be L6 or L7 IC, no problem. No managerial duties whatsoever. L7 is more nebulous, but L6 is absolutely doable for anyone with a modicum of marketable skill.
You see, in spite of their internal promo treadmill and brainwashing, companies have to compete on comp regardless. Comp ranges, in turn, are tied to levels. If, say, someone who knows a distributed query plan from a hole in the ground costs $1M/yr, they'll get that and the "level" will be adjusted accordingly, as much as necessary, ignoring the elaborate formal descriptions of job responsibilities.
It's the proles in the trenches that take the levels seriously. People who actually run things understand that levels are merely a hamster wheel, put in place to give you something to look forward to, and to keep your comp expectations in check. Lack of "broad organizational impact" is _the_ most often used cudgel to deny promotions to the more senior level, unless your skill stack allows you to bypass this bullshit entirely.