dd15 air tank system question

2017 cascadia with dd15. The engine oil level varies with air bags suspension deflated. It is not a significant variation nor has any issues, but is something that is noticeable when inspecting fluid levels with suspension up or down. Engine runs fine with no codes.

Primary tank check valve has been replaced which is the one with a round object inside.

Thanks for your help. If anyone is familiar with this observation please let me know what you think the issue may be, if there is one at all.