Solid Hardwood, Engineered and Laminate Flooring - Securing Vs. Not Securing Subfloor

hi i am new at this whole posting a thread deal and I hope i am getting it right.

I have gotten my hands on some used oak hardwood flooring that I plan to install in my unfinished basement. The system will be.

3/4" oak hardwood
nailed thru the tounges to
3/4" plywood
resting on
dimpled polyethylene sheeting (DELTA)
resting on
basement slab

What I have been wondering about is the need to fasten the plywood to the concrete slab. I am concerned that using power actuated nails or tapcons or other such fastening systems will unnecessarily damage the slab (which is already cracking and spalling) , as well as create entry points for moisture.

will using T&G plywood or securing the edges of the plywood with buiscuits allow me to avoid fastening the plywood to the slab ( in essence using a floating subfloor system )

I don't completely understand why I have to fasten the subfloor to the slab, as the hardwood will be nailed thru the tounges to the plywood at 6" intervals in any case. I am probaly not taking something into account, but I wouldn't think the floor would be going anywhere.

If anyone could enlighten me on this subject I would be very grateful

It is not recommended that 3/4" solid hardwood be installed below grade in basements due to dimensional instability. Moisture and humidity issues tend to be major issues in basements and hardwood does not do well there for that reason. Engineered hardwood can be installed in basements.

Open window. Take cash and throw it out.