Is there any truth to the maple story?
Yes, but they also sort the logs and then grade the ply accordingly on top of all that, but being able to sub in layers of local maple reduces cost for them as well.
Re water based glue is better for the environment and for the human doing the work, epoxy banned from many countries (I thought) because of the harmful properties.
Epoxy makes it stiffer (Dwindle boards are very stiff) or from epoxy vs glue:
Epoxy has the advantage of being waterproof and does a good job filling gaps in wood. Most other wood glues will not hold well if there is a gap between the pieces of wood that you are gluing together.
Epoxy is more aggressive than the normal water base glue, which is the industry standard. Since Epoxy is so strong, less of it is used yielding a considerably lighter and stiffer and longer pop.
I am sure others would know more or have better info too.