If you are referring to wood trim at the head of the window and there is some kind of siding above it, it is critical to install a piece of preformed metal Z flashing with the longer upper leg under the siding and weather barrier (Tyvek, etc.) and the smaller lower leg over the wood trim. Without it water will simply run behind the head trim and cause it to deteriorate. Nothing could be more standard or elementary in the design of a house. The larger question is whether or not the builder is competent to complete the house without professional oversight. Here is a link that might be useful: head flashing

A foot of flashing tape around the opening would be complete overkill.There are several steps that should be taken in proper flashing (back-caulking the nailing fin, closed cell foam, window flashing tape, metal drip cap/head flashing, etc) that will offer several steps of protection. I'd give the "technical" rep the opportunity to explain those issues to you. On the Renewals, if you chose the woodgrain interior be sure to keep moisture off of it as it will be adversely affected if you don't, and that warranty is only 10 years. You really want to treat them as you would real wood windows IMO.

Our contractor is in the process of replacing our windows w/ new vinyl windows - new construction type w/ fins. The "flexible flashing" material used around the window/ jamb appears to be a double-sided kraft paper with a thin layer of asphalt in between, in fact, it appears to be Fortifiber Aquabar, apparently intended by Fortifiber to be used as a vapor retarder for floor installation. The windows do all have a full drip cap metal flashing above them. This aquabar flashing was installed in the way that flexible window flashing seems to be usually installed. (The house sheathing is mostly covered by felt, and, in some areas, housewrap) This is an experienced contract/ remodeler with an "A" angie's list rating in our area, who has apparently used this material in this way without problems in the Portland area. However, I'm concerned because all I've ever seen used this way is waterproof flashing. At any rate - I would appreciate any comments.

It looks more wood-like than capping, but I am not sure anything looks exactly like wood if you are talking about having some grain to it. There are textured PVC and LP trims that look great and very "woodlike". Just depends on the look you are trying to duplicate. If you are wanting rough sawn cedar, there isn't much that will duplicate that look. That said, cedar should last.