I'll plead guilty to that. Remember, the first driver of scope is intended use. If the client's intended use is to make a real property decision aided by $150 worth of independent third party analysis, and this is an institutional client - so be it.
As to the original post, it may not require anything more than about 7 calories of additional market analysis. That is, if you are just sending along comps 4-6 of the original analysis, a second full analysis is not necessary. However, the sticky part in my mind what AO-3 calls "simply a new assignment" aspect. Comps 4-6, like any other "comp check" (or more), are assignment results created as a consequence of an agreement with a client. So, for starters, you are probably going to want to incorporate the orignal report by reference to get as much of Std 2 out of the undertoe as possible. But the part that seems really tricky is explaining the intended use of the request for additional comps. Among other things, it seems like looking for comps to support a value that has already been determined.