Starnge sound / dealer solved/ emissions blow out

2015 DCSB Tacoma Sport. Due to the warmer weather and having the windows down I noticed that when I turned off the truck I heard a whirring noise. To me the sound was like a bad starter spinning but fainter. I only hear it when the truck was turned of in the garage and the windows down. I called the dealer and the service guy transferred me back to a mechanic and he said it is the exhaust/ emissions system blowing out the raw fuel and exhaust when the truck is turned off. I told them I had a 2011 with the same configuration and it didn't do this and he said it was something new and I'm not the only one they have heard from.
Anyone else notice this ?

 

yes, totally normal