does this simple sentence make any sense.

It's ambiguous, but it seems to mean that there is a question as to he having done the work.

Un huh. It appears to state a certainty, but leaves a lot of room for doubt.

Yes, the sentence is correct, and has meaning. Such a sentence would be used to reply to someone who expressed doubt that the subject of the sentence had done the work in question. Unless you wish to express something else, there is no reason to change the sentence.

I sent Bill out to clean up the job site on Friday, but i don't know if i can count on him.

He was sure to have done the work.

It makes perfect sense in such a context.