"And, as a practical matter, it's worth knowing that no future buyer
can prove or disprove the results of a construction engineer's
findings or your knowledge or lack thereof. "

How about if the new owner happens to later call the same engineer and
the engineer says, "Oh, I remember looking at this house last year and
giving the owner a report!" Doh! Or how about if the new owner sues
the seller and the seller has to give a deposition? Now would you
advise the seller to lie under oath, and risk perjury charges, to try
to maintain the coverup?

Granted, it's not highly likely that a future owner can prove what you
knew about a problem, but it certainly isn't a sure thing.