Yep, I'd heard about that delayed onset phenomenon as well.
Looks like the last two lines of this article tries to reconcile that
with the "steeper decline" in the more educated folks.
An extended family member is in decline with Alzheimers...but
she is one of the type that can talk to you, "read" you and carry on
rational talk for...awhile.
She totally suckered her daughter and son-in-law for a couple of years
until they got her in for a full diagnostic work-up.
Yeyp, my Mama was good at 'hiding' it for a while, too, but it eventually caught up with her.