just because it is a Macro lens doesn't change the DOF you get from a 100mm non Macro lens to a 100mm Macro lens.
That's what I thought.
If identically framed for both 100mm lenses, then yes the DoF doesn't change. But comparing the 100mm macro with the 135mm at the same framing, DoF should be less with the 100mm macro.
For most uses the 100mm macro should be able to replace the 135mm. Comparing the two -
IQ - similar
100mm macro benefits - shorter MFD, 1:1 magnification, Hybrid IS
135mm benefits - longer reach, 1 stop faster
So unless you're a sports shooter, you can simply walk up closer to your subject and turn on IS to negate the 135mm's reach and 1-stop advantage.