$MaxPiecewiseCasesgives the maximum number of cases to allow in explicit Piecewise objects generated by expanding any single piecewise function.
Floor is not converted to Piecewise because the number of piecewise cases exceeds 100:
This increases the limit on the number of cases to 200:
Now PiecewiseExpand converts Floor to Piecewise:
This reverts $MaxPiecewiseCases to the default setting: