Background blur missing with HDR CompositeMode 1

UPD: According to Affects Version field, issue reproduces in 4.26, Regression for 4.27 - No.

Download licensee repro here - [Link Removed]

1. Open the project, open the BasicBlurMap, press Play.
2. Observe that the background blur is present.
3. Enter command r.HDR.EnableHDROutput 1 to enable HDR output (even if it's not really supported)
4. Since we're working with engine defaults, composite mode should be active already, if it isn't enter command r.HDR.UI.CompositeMode 1 as well.
5. Observe that the background blur is gone.
6. Enter command r.HDR.UI.CompositeMode 0.
7. Observe that the background blur is back.