HDRP and Shader Graph: What color channel used for height by "Parallax Occlusion Mapping" node?

Using HDRP and Shader Graph:

What color channel is used for height by “Parallax Occlusion Mapping” node?

Need to pack multiple channels into one map, and currently packs Metallic, Occlusion, Height and Smoothness into RGBA.

Hm… seems to read height from red channel.