Hey Guys, I'm new to the forum ( I've read the rules, I promise! )

I'm a home owner, and the other day, our HVAC group that installed our new A/C and furnace came out to do a PM checkup on us. The installed the Furnace in 2011 and A/C in 2010 ( same installers ).
Anyway... the Furnace is a Bryant 315AAV (110,000 BTU 80% variable speed )
The A/C is a Bryant Preferred Series 127A I think, which I believe is 3.5ton, but I'm not at home right now to be able to be sure.

We have a 2850 sq foot house above grade. We live in the north of Indiana.

When he was doing his PM, he saw that we have a 5 ton blower installed, and said that it should be turned down because we only have a 3.5 ton A/C.
I wasn't home at the time, my wife handled it so I wasn't able to ask any questions.

He did go ahead and turn it down. I honestly haven't noticed any difference ( well, obviously difference in airflow )

He said it would cool better, but I'm afraid I don't understand why that would be true. Wouldn't more airflow increase the efficiency of the heat transfer?
I could see it costing more electricity to run the blower faster, but I don't understand why that would make it cooler.

I understand why having an oversized A/C is bad, but why is having an oversized Blower bad?
Can anyone educate me on the plusses and minuses?

Also, in the winter won't this blower now not be properly sized with the Furnace?

Thanks very much for any advice and education you can give me!