The NYTimes article covers the issue well. The remnants of chemical weapons were not handled well which resulted in american casualties and which resulted in potential(I would say actual) use as IEDs. So Pentagon has reasons for not wanting to talk about this. I know mustard gas preserves fairly well. VX and sarin does not.
So there is no thinking in the line of ' Saddam had chemical weapons after all'. At least not anymore. Before the war there was deliberate obfuscation on the subject of how much chemical weapons capability one needs in order to provide a reason for war, so any find of a weapons cache was considered proof.
The idea is still around but officials have dropped it long ago.
That was so important about the work by Scott Ritter in the runup to the war. He quantified the possible capability and made clear that whatever capability there was it could be military significant. So instead of asking 'are there chemical weapons' he asked 'are there enough chemical weapons', which is what every military analyst should do. An important part of propaganda is making you ask the wrong questions.