Why is Simulink outputting a 3D array in some, but not all, "to workspace" blocks

I have several "to workspace" blocks, all set up with Save format set to Timeseries. In all cases, the output is stored in a structure. Several are 3-vectors. In some cases, the .Data dimension is number_of_samples x 3, but in other cases it is number_of_samples x 1 x 3.

I've tried using the squeeze function, and it sometimes works and sometimes does not.