[DCP-o-matic] Default colour space changed in 1.79.0

Hi all. While teaching a group of people how to use DCP-o-matic last weekend (DCP-o-matic is now on the syllabus at London Film School!), I came across the change in v1.79.0 that default colour space conversion is now Rec709. For the majority of the people who'd brought their film to test on, we found that sRGB was the best setting for them. We were comparing their source files (mostly Quicktime) to the resulting DCP viewed in Doremi Cineplayer (evaluation version) and found that Rec709 was changing the colour balance of the image (most notably, making it darker). What was the rationale for changing the default to Rec709? And is there any way to examine a Quicktime file to find out what colour space it's in? With shorts filmmakers, they often don't know themselves! Presumably the default output from Final Cut Pro, Premiere Pro etc remains sRGB rather than Rec709? Many thanks, Jim