Just wanted to let you know that I have referred the matter to our development desk for review. I designed the member in the latest 20.07.11.70 version of the software, and STAAD.Pro does calculate the compression capacity correctly as 40.3 Kip in line with what you mentioned in your first post. Please see the highlighted portion below.
I am trying to figure out why the ratio is then going up to 2.605 as per H2-1. The flexural terms should be zero and so we should end up with a ratio close to 1.12 as per my calculations. Either me or one of my colleagues will get back to you soon on this.