Greg Esres wrote:

... except for the rules of arithmetic, a total being the sum of the
various categorized flight times.

Still just speculation on your part. There is no reason to think that
the listed categorized kinds of time are exhaustive.

Fine. He can invent a "was a helpful passenger" column/category in a
log book, and add it there, and thence accumulate into a "total".

The person the OP mentioned got valuable experience, but which may not
fall into any official category. [...]

That's true. Nevertheless, if the person is proposing to use this
valuable but unofficial time in furtherance of ratings or insurance
experience credits, he had better discuss this with the respective
agency, lest he be suspected of fraud.

- FChE