Utter nonsense.
I work for a company that is wall to wall engineers of almost every kind. Thousands of engineers located on all three coasts and many states in between. Structural engineers, mechanical engineers, electrical engineers, software engineers, hardware engineers and much more. Not one engineer uses the word "datum".
And it's been that way for many, many years.
Wow!
Falling back on appeal to authority, and elephant hurling!
Laughable.
Real engineers use datum in proper context. Data, as the plural of datum is frequently used in statistics, or in a database field with multiple records, but multiple sources of datum are used in multivariate expressions, such as singular records of multiple fields.
Many designers confuse and interchange the two words.