I was taught the same.  I guess maybe it depends on how you define "remedy the shortfall".  I would take that to mean that you "catch up" in the year of discovery.  But since we can no longer decipher "under 24" or "you" in the tax code on our road to Idiocracy, who knows how one might interpret "remedy".

From the instructions:

Waiver of tax for reasonable cause.
The IRS can waive part or all of this tax if
you can show that any shortfall in the
amount of distributions was due to
reasonable error and you are taking
reasonable steps to remedy the shortfall.

Rick