The results in the article rely on details which are specific to the version of Windows and to the debugger which is present at the time. They have not been documented widely because they are so unreliable.
Windows will inject a thread into an attached process in order to gather information about the process, which led to the "DebugBreak overwrite" technique to defeat it.
There are additional checks which are performed when a debugged process is launched, which can result in altered stack state, but the whole thing is just chasing ghosts. The behavior of Windows could be changed at any time to reintroduce the behavior or change it in yet other ways.