There are literally hundreds of T-Birds out there that are FG over wood - many of them still going strong. The technique has merits especially for the homebuilder. I think it's much better suited for plywood sheathed hulls as the ply is a fairly stable material.
Fiberglassing over conventional plank on frame hulls can be more problematic as these boats have some inherent flexibility that may not sit well with a relatively thin fiberglass layer (probably added to slow down leakage?!)
Being fiberglassed only to the waterline seems to be asking for troulble - abrasions and stresses could allow water seepage under the layer of glass (I'm picturing sheets fiberglass cloth slowly peeling off the underbody one day....)