Makes no sense to not glue the biscuits, IMHO, unless they are such a
tight fit in the groove that, on swelling after getting wet, they
distort the piece enough to be seen.
This might happen in balsa, or where you glue it, finish it, and ship
it. Without any scraping, sanding, planing, whatever. Unlikely enough
to be irrelevant.
Every bit of joint strength is valuable.
Norm still abuses brads.