Item category T does not allow good receipts and does not allow invoice receipts.
Which is good if you get all your cost center procurement for free, which I do not believe.
If you want restrict the use of a material number for accouont assignment category K, then you have to use a BADI to control that.
I personally cannot understand such requirement, as a material master is a template that is used to make order entry easy as a lot data will default automatically from there. further it makes procurment for the same item look equal, without material master each PO will be somehow unique, you cannot even garantee that the users choose the right material group