C.B. Zeller, I have always found these two sentences confusing. The first sentence excludes qualified and nonqualified, but of course qualified plan distributions are not 415 comp. But then the next sentence says you can include nonqualified deferred comp when it is received, which is directly opposite to what the part of the first sentence that applies to nonqualified deferred comp says, and then says, but only if included in income, which is close to saying , "only if you comply with the federal income tax law", and "only if the plan so provides." Just horrible drafting, I think.
If the plan uses a W-2-based safe harbor definition, the plan will so provide. So it's really the equivalent of saying nonqualified deferred comp is includible when distributed, unless specifically excluded by the plan document. If you are using the classic safe harbor, which the language you quoted is part of, I think, then it is probably excluded, but if you are using W-2 based safe harbor, it is almost certainly included. There is a separate timing rule, which you have not quoted, i.e. the deferred comp that is included must be includable whether or not the employee has terminated employment, i.e., it must be deferred comp that pays out on a fixed date or upon a performance goal, which would likely be the case for phantom stock or units, and not deferred comp the distribution event for which is separation from service.