...I looked at Crucial's website and found that they've apparently undergone a change in policy and no longer sell RAM upgrades that surpass Apple's specs.
Apparently Crucial now hides any ‘off-label’ options more consistently...
Am I the only one who remembers that Crucial originally did
not offer RAM upgrades that exceeded Apple specs? I more than once bought from 18004memory or OWC when upgrading older Macs, specifically for that reason. I'd call it a return to a previous policy, not the advent of a new one.
See for example
Pushing the HW envelope with OS X...