I think you're right that Thiel did not officially claim anything about the 3.7 being easier to drive (phase angle closer to zero) than previous models. I believe I got that idea from a non-quantitative statement by Thiel's customer service rep, Gary Dayton:
http://www.thielaudio.com/weblog/2006_10_01_archive.html
The published specs say the impedance magnitude dips to 2.8 ohms, but there's no spec regarding the phase angle.
http://www.thielaudio.com/weblog/2006_10_01_archive.html
The published specs say the impedance magnitude dips to 2.8 ohms, but there's no spec regarding the phase angle.