Trading API for PS4

Hello guys, I want to begin by saying I'm not tech savvy so I don't actually understand how API works but I have a few questions and an idea.

1. I looked around a few PS4 profiles (playing on one so that's why I choose PS4 but I guess XBox works the same way) and I noticed that on some appears the stash tab but not actual stashes and some doesn't show the stash tab at all. Now, I'm guessing that's because of the private settings of the profile.

2. Where is the trade API reading from? It is not reading your public set stash tab showed in your public profile?

My idea is that, if possible, the public stash tabs will be showed in the profile and the API should be able to read those tabs and, well, show them further to trading sites/apps.

I read a discussion some time ago stating that PS4 servers cannot be interrogated by the API so that's why the public stash tabs cannot be seen in trading sites but if the API reads the public set stash tabs from the POE official site profiles?

I'm sorry if I'm not clear on what I'm asking but I am willing to explain further.