The answer is currently.... I don't know. It is set properly as it was in the other styles. I have submitted a ticket and am waiting to hear back. It might be a bug in the new software, since it is set the same.
Any updates on this? The only style that has an Arial font for me now is the SatelliteGuys Classic. Notice that it is only in the message, not in the signature or below.
Classic:
1.4.2: