That sounds like you wanted to request things like Osmium, Platinum, Bromellite,Alexandrite, etc. - the mining-only commodities - rather than any sort of materials.Perhaps I misunderstood. We asked FD to only take those mining-mats that cannot be bought anywhere, so probably there will be mineable commodities too. We do not yet know which though and what FD made out of our proposals. The problem with the "mined-only"-flag is, that with it present people will have problems with the wing-mining mechanics. Cause the materials cannot be exchanged between ships without losing the flag afaik.
(If they give you the mining-only materials - Boron, Lead, and Rhenium - you will not have a fun CG)