Intel (and everybody else) does this for good reason .. high endurance components (Milspec, server, whatever) are usually designed for tolerances far beyond the actual spec, because manufacturing issues can cause the tolerances of the finished product to deviate somewhat.
If they design a [gizmo] to operate at 1.5ghz and sell it as a 1ghz chip knowing full well there is plenty of overhead but chances of failure running it at 65% of design are pretty much nil, yay for them for meeting the rejection rate.
Then along comes marketing and says "hey, we can sell the rest of them at 1.5ghz as consumer units" .. and the failure rate there doesn't really matter as much because you just print a disclaimer about "your data may go poof" and RMA the broken ones. As long as the defect rate is low enough to remain profitable, yay again.