How to correct possible subfloor l/360 deflection under live load, when basement below is finished
Typical requirement for US building codes is l/360 live load deflection limit. So it is not quite accurate to classify this as a correction if the design deflection is l/337.

If the finish material requires a stiffer floor, then a structural change is required for aesthetics and or performance, but not for structural safety. Structural modifications will normally require selective demolition of finishes whenever structure is not exposed.

The options are:


install the tiles with l/337 deflection and live with the possibility of aesthetic and or performance issues.
expand the project scope to modify the structure.
select a different floor finish.