We almost never put detectors under the floor anymore, but if you are being directed to do so, is it for activation of a suppression system?
I would have to dig to find it, but I think the fire code requires detection associated with suppression activation being required to be in raceway.
Edit - My memory was from 1 RCNY §4000-06(C)(3)(iv) which said In any suppression and extinguishing system activated by automatic
fire detection, including but not limited to pre-action sprinkler, deluge sprinkler, clean air agent, halon, range hood, carbon dioxide and dry chemical, multi-conductor cables shall be installed in RMC, IMC, or EMT. - THIS WAS REPEALED.
Electric Code Section 760.52 is for NPLFA cable was added and 760.130 covers PLFA, but does not generally require raceway for suppression applications.