Not unexpected especially if some of the time the engine is running, you're stopped in traffic.Seems a little low.
You would figure the engine wouldn't run so rich while cold (30 degrees F) - (more fuel = lower combustion temperatures). Only drive one or two miles in ERDTT (for about 5 minutes) but, what a hit to MPG.
I'm thinking the gas "guess-O-meter" may be off and needs to recalibrate.
Also, you could always change the setting under Engine Assisted Heating in the Config menu to "Deferred" ... when this is done, ERDTT will only occur when colder than 15F, rather than the default 35F.