2015 t590 without tier 4 engine?

Hello everyone. I am purchasing a new loader from my local dealer for our construction company. Of course I been trying to do my homework on the new loader and when I was asking my sales rep about tier 4 engines he said the one he is having delivered has the kabota engine (non tier 4)? It was my understanding that all 15's were tier 4. He told me that the government gave Bobcat x amount of credits for selling so many tier 4's. This allowed Bobcat to use up some of the kabota engines they still have...?

I guess my question is has anyone heard of this? I tried researching it myself with no luck. Thanks!