Are you try to connect TWO devices in one WPS PBC session ?
If answer is yes, I remember it is not allow in WPS spec.
Yes, I try to connect two devices at the same time. That's not allowed, but it's a test case for error conditions.
I did't expect that its work. But in both cases it should be reported as an error, I guess.
Yes your test is correct. If two devices are in WPS session none of them are paired and there are no error messages.
Normal use case is to enable one device at a time to pair with AP.