On Sunday, January 14, 2018 at 6:22:14 PM UTC-8, DerbyDad03 wrote:

Bottom line: Are you saying that the surfaces created by a straight router
bit on the edges of two 1 x poplar boards is too smooth for Titebond III
to perform its designed task?

Yes, there may be something to that. A blunt (carbide) bit both cuts and slightly
crushes the wood as it passes. That crushing closes the ends of the wood
fiber, and makes glues less effective.

For high quality veneering (and plywood) the surface quality from an
acute (low-angle) plane, or from light sanding, is preferred for glue
bond. D-day gliders, manufactured in quantity, were all sandpapered
before assembly and glue-up.

Titebond recommends acetone wipe for oily woods, and
" A good bonding surface can also be achieved by sanding or planing the wood just before gluing the joints."
but there's no harm applying the same advice to poplar.