The flex connector must be rated for the application. Some are for indoor use only.
There was a refrigerator 16" in front of this furnace otherwise I would have gotten a better picture. I find it funny that a few days after this post I run into one like it. Except rather than use a nipple, they used a coupler. As you can see, they did put the coupler where it penetrated the cabinet. Reason for me being here? Bad gas valve. Replaced the valve, used a whole two street 90s and one 12" nipple and this issue has been corrected. Yes, I did add a sediment tee outside the cabinet.
Were are the AFTER pictures ? :grin2: