Glue-Assist Nail Down really necessary for wide plank?

Hello all. I'm replacing carpet with wood flooring on 2nd floor of home, and have questions about the recommended install method and underlayment.

I'll be installing 3/8" x 5" pre-finished hickory engineered wood. The manufacturers instructions that came with wood say to install by glue-assisted nail down for 5" wide or larger planks (running bead of glue perpendicular to floor direction every 12" oc).

I had planned on using an underlayment like Quietwalk Plus or Eco Ultra Quiet Premium under the hardwood to try to reduce impact noises being heard on 1st floor. With the glue-assist method I have to eliminate the underlayment and attach wood directly to subfloor though.

My question then is it really necessary to use glue for 5" wide planks? Or will the flooring still be okay if I eliminate the glue and just nail down over the sound dampening underlayment?

Subfloor is planks at 45 deg angle with 3/4" plywood underlayment on top. It's all structurally sound and flat.