Color Space Transform - Apply Forward/Inverse OOTF?

Hi,

The Resolve 17.4 manual doesn't seem to describe exactly what the Resolve FX Color Space Transform Advanced settings "Apply Forward OOTF" and "Apply Inverse OOTF" do.

As a sanity check, I tried the following settings. Now of course these are not typical color grading settings. I have selected linear gamma only to understand why the following happens:

Project color science - "Davinci YRGB", timeline color space - sRGB / Linear
(i.e., color management effectively bypassed with timeline gamma = 1)

Then I add a Color Space Transform node in the Color page:
Input Color Space - sRGB
Input Gamma - Linear
Output Color Space - sRGB
Output Gamma - Linear

Check "Apply Forward OOTF" -- video levels go down.
Check "Apply Inverse OOTF" -- video levels go up.

Why do the video levels change? Since Resolve color management has been disabled and there is linear gamma everywhere (seemingly), what conceivable transform could be applied at this point?

Again, I realize these are not realistic settings -- I'm trying to get a precise technical (engineering) understanding.