It has always been this way. The acceptability of a doff for grinding doesn't depend on whether or not it is bound, but some arbitary characteristic. Doffs from Ferra and his KDF equivalent cannot be ground. Entertainment holograms and a few other special doffs like Helna are also ungrindable. But regular bound doffs, such as Supports, have no problems with degrinding.
Although why you would fall for that "Underperforming" upgrinder schmuck bait is beyond me. That one is a ripoff.
The dil cost for some random thing. Yes it is cheaper than buying a DOFF from the store, but that is because you are effectively doing the DOFF lottery, whereas if you buy a DOFF from the store you get the one you want.
You could put in five security DOFFs for example thinking you will get another security DOFF and end up with a bar tender which could be useless to you.