I see your point, but the front has been altered as well, with the material blocking more high frequency sounds from 90º and beyond, possibly less than 90º depending on the accuracy of the deployment. Depends on the size of the capsule housing, and I don't personally know this mic.
Refer the photo in the original post. The front of the diaphragm has not been altered. It is not covered by the same croakie material. But the reason I suggested the OP might consider pushing the microphone further into the croakie, or placing a piece the same croakie fabric in front of the microphone, is as an attempt to bring the differential system back into its intended balance by providing the same filtering to the front of the diaphragm as has been applied to the back of it. In this highly simplified conceptual model at least, the filtering is the same to both sides of the diaphragm, the difference cancels out eliminating the altercation of polar pattern, leaving only the filtering effect on overall frequency response (similar to use of a windscreen covering both the front and the vents).
It now occurs to me that you may be referring to the
absorption or
diffraction of sound around the bunched up portion of the croakie. Those are quite different mechanisms of directivity, briefly touched on here:
Consider the balls and baffles used to make omni mics more directional in the highs.
That is a very different mechanism of directivity. Ignore the bit about mounting near one's head for the moment (which does constitute a baffle) and consider just the microphone with croakie material covering the vents, verses not having them covered.
Those mechanisms will have an effect, but will not apply in the same way they do for an omni. Because they affect sound arrival to both the front of the diaphragm and it's backside via the vents, their effect is overly complex to try and speculate about here. It's complicated!
Just the vent-covering aspect on it's own is not very predictable, but at least we can analyze that as a simplified system which is what I've tried to do above.