I don't see how an appraiser can complete the 216 without developing an indication of market rents.
SOW, IMO, addresses that.
Client wants an estimate of expenses. Appraisers can do that all day.
I'm fairly certain I have had a few (less than 5) of these types of requests in, say, the last 5-years. I provide an expense and replacement estimate and state that market rents are not part of the analysis. Sometimes, the house was owner-occupied.
I don't see this as a big deal (again, that's me).
Certainly, if we are going to develop market rents as part of the original appraisal assignment, that is more work.
If you get a request for this type of assignment as a stand-alone, and then develop market rents to complete it, that is an appraisal (and you'll have to have all the reporting requirements of SR2-2a that are relevant).
Otherwise, I take it for what is being requested:
Client: Denis, can you give us an estimate of operating expenses for the subject property?
Denis: You just want the expenses; you don't want an estimate of market rent?
Client: Yes, we just want the expense estimate.
Denis: I'd be happy to. The cost is $X.
Client: Great, and thanks!