Under Reg. 1.199A-6(e)(2)(ii), the fiscal year pass-through entity calculates QBI, W-2 wages, UBIA of qualified property and the aggregate amount of qualified REIT dividends and qualified PTP income for its full fiscal year ending after 12/31/17 and the shareholders treat them as having been incurred by the individual during the individual's taxable year in which or with which the pass-through entity's fiscal year ends. 

It may seem somewhat generous rule, but remember that the pre-2018 PTE income is also not eligible for the DPD deduction under the former Sec 199. And when these rules expire, the partial year PTE income of 2025 in the fiscal year that ends in 2026 will not be eligible for a Sec 199A deduction either.