Depth buffer / GBuffer size

Greetings! I had a question regarding memory allocation for the Depth buffer and GBuffer.

According to documentation https://blogs.unity3d.com/2018/03/16/the-high-definition-render-pipeline-focused-on-visual-quality/ , "HDRP uses a dedicated render target allocation system that avoids recurrent reallocation when resizing the screen". Which is exactly what I observed when examining the size of one of the GBuffer layers. Namely, resizing the screen (so long as the new size is not larger than the original) does not change the size of the GBuffer textures, so essentially HDRP renders into smaller patches of GBuffer layers.

Conversely, Depth buffer is always reallocated.

I was wondering if someone by any chance might know what could be the reason for such architectural choice. I would greatly appreciated if someone could help me fill that gap in my understanding.

Unity version: 2018.4