Assuming a USA project (you might specify which country you are in)....
The IBC has equations for estimating diaphragm stiffnesses and both the IBC and ASCE 7 have definitions of rigid vs. flexible diaphragms that depend on the building size, aspect ratio, etc. - diaphragm deflection vs. shear wall deflections (per MotorCity's comment).
The trick in your case is that you also have a T&G decking under it which certainly adds to the diaphragm stiffness above and beyond the plywood by itself.
There have been posts here on E-T that mentioned new information on T&G decking shear capacities and stiffness - do a search.
You might then have to estimate each and combine into one overall shear stiffness (G') and then see how your diaphragm rates vs. the shear wall deflections.
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