Oh, I see. The automatic modprobing in 1.3 also happens during a normal tce-load.
It's meant to remove the need to manually modprobe, whenever possible. It doesn't remove the possibility to manually modprobe.
edit:
Here's an example:
Say I have a pci wlan card that doesn't need firmware, maybe a Ralink rt2x00.
In TC 1.2 and previous I'd need to modprobe the module myself, after loading the extension.
In TC 1.3 and onwards it's enough for me to load the wireless extension, and my wireless hardware becomes blinking and usable