Reproduction steps:
1) Download and open user's attached project
2) Switch active platform to Android
3) Run "Test.unity" scene in Editor
-- Notice that "Source Format: ARGB32" is being printed regardless if HDR on camera is turned on or off
4) Change platform to Standalone and press play
-- Notice that "Source Format: ARGBHalf" is being printed if HDR is turned on

Expected result:
Android platform should also return ARGBHalf when HDR is turned on

Note:
This issue is also reproduced on devices. Both editor and device do support ARGBHalf (checked with SystemInfo.SupportsRenderTextureFormat (RenderTextureFormat.ARGBHalf) method)

Reproduced with:
5.4.0f3, 5.5.4p1, 5.6.2p4, 2017.1.0f3, 2017.3.0a2

Reproduced on Editor + Android platform, Editor + iOS platform, Android and iOS builds.