The change that i propose is minimal,in "Parallelization" set "spatial overlap to 2, instead then 0

The reason is that are many filter that use as component [Anisotropic]" , and now some (as example Harto "Dream Smoothing") are malfunctioning as side effect of the default for "Parallelization "
using the filter a stripe in the middle remain unchanged as was unselected

Now seems easy update the "derivative" filter to incorporate the option , anyway i believe a minimum of overlap as 1 or 2 will solve...and also give a nicer first experience when using asinotropic smoothing , the "unedited" stripe is often too small to be visible in the preview but at bigger size screw up the result also because is in the middle.

i believe just change "overlap" default, from 0 to 2 (2 to be safe, 1 seems sufficient in most cases, 0 is too often delusive for a default) will solve.

I believe could be a even better solution in a future but here will be OT, i will post it on the
Parallelization topic

The overlap is already by default to be 32px wide.
Which filter has a different setting ?

Apparently Harto "Dream Smoothing" :
it show the same type of unedited strip in the middle that may happen using Anisotropic Smoothing with default Parallelization option, that on my copy of gmic for Smmoth [Anisotropic] seems to be 2 cores and 0 overlap ...obviuosly i refer to the plugin

I imagined that was the cause because "dream smoothing" is based on anisotropic smoothing
and since was created before the new Parallelization option, i suppose it use the default

But anyway was my supposition ,yet i still see the default for overlap set to 0 in Anisotropic Smoothing not to 0,35 and i am sure i didn't modify the default

Yes, before, there were an option to use "tiles" which has disappeared and replaced by the parallel options instead.
You should explicitely ask for Arto to update his filter, as the arguments of the -gimp_anisotropic command have changed.