That's different.I just bought a 2014 volt with one year left on the warranty. The dealer told me and I have in writing that the warranty is good from the day first in service, in this case Sept 2014 till Sept 2017. I have the full warranty till then, not prorated in any way.
What he's describing is if you bought that 2014 brand new (never used) today, it would be minus 22-23 months.
Yours gets the 3 year warranty from original in-service date, which was Sept 2014 for your vehicle.
I've never heard of this before, but if true it effectively means the warranty begins on Jan 1st of the year following MY (i.e. 1-Jan-2015 for a 2014 MY, expiring 31-Dec-2017 regardless of when it was actually put in-service)