The reporting of QBI, W-2 wages and UBIA for each trade or business by an RPE (relevant passthrough entity) is required by Reg 1.199A-6. Also that regulation says if an item is not reported on the K-1 by the partnership (i.e. Code Z, AA, etc) then the owner's share of each unreported amount is presumed to be zero.

So it seems as if the IRS intends to disallow deductions for QBI on pass-through entity income if the entity doesn't explicitly identify on the K-1 that it there is QBI. A partner won't be allowed to assume income is QBI.