[HDRP 10] How to correctly write custom PP for BeforePostProcess injection point?

No matter what I do, TAA becomes completely broken. In previous version (8.x) everything worked correctly. What changed since then?

I just took GrayScale effect from the documentation (so there is only color buffer sampling) and set the injection point to BeforePostprocess.
Everything works correctly if I set PP to AfterOpaqueAndSky injection point.