From the HD Fury forums I believe that if you do send an EDID with HDR metdata that has only the first elements of the EDID up to the PQ value and everything else on the EDID being 00 then the TV/projector will fall back to its native luminance level (to tone map to it’s native level).
From my experience, the forum below has been the one that has drilled down on the use of EDID for HDR metadata and DV block for a number of years using HD Fury devices. The post number 5074 uses a way to send the minimum HDR metadata for a TV/projector. Notice that both HDR metadata and DV block are sent. For this post the HDR metadata is the one to notice since the DV block was for a projector mainly (lowest luminance levels). From the debate on this issue it seems that some devices (TV/projectors) use the HDR metadata and others do not - so ymmv.