Frank,
I followed pretty much that exact train of logic for previous fretjobs, but I haven't experienced any problems with the unattached fretboard technique. Yes, the board will backbow, but the caul it is taped to keeps it dead flat throughout fretting, and the bow is easy to push flat with one finger - it is totally removed from the equation when you clamp for glue up. The trade off is not having to support the neck whilst you fret.
Basically, your fretboard is flat and true, with the front and back parallel. As such, gluing the board to a dead dead straight neck, can only result in a straight board.
The order I did my last neck was:
1. Taper neck and board with the same template, clamp in position and drill positioning pins at 3rd and 17th frets.
2. Remove board, and clamp neck to a flat 2 x 4 to rough shape the two ends with a rasp and scraper.
3. Glue neck to body, route for neck pickup, using the still square neck shaft to clamp the pickup template.
4. Inlay board, dress flat and polish inlays with a radius block and varius grades of sandpaper. ( this is when I would have added the binding if I'd used it on this neck).
5. Fret board, flush trim and bevel fretends.
6. Glue on board, using the positioning pins to get it prefectly aligned.
7. Shape the rest pf the neck, joining the two ends with longs flowing spokeshave strokes.
Like Franks said, I'm not going to question any method which has proved effective for other folks, I simply wanted to address Derek's statement that you 'always' want to glue up first. That is a tried and tested order, but it isn't the 'only' way.