I am definitely more flexible since losing weight (30kg and counting). Is this simply from having less volume to bend around (!
), or are there other mechanisms going on here?
Flexibility is important to me as I am a runner… so this is a great thing! 
♂
Your body is becoming stronger and more efficient (yes less volume too).
Keep going it gets even better! 
It sure does. I actually started feeling this when I dumped all my water at first. Just that alone had an effect, and it’s just better.
Funnily enough fat people are often very flexible! (Myself included, I went to a friends yoga class a couple weeks ago, she teaches it, and I could go much deeper into many poses than the thin women in the class) In fact, fat people have to be careful when doing stretching exercise to keep from overextending, because it’s easier when there’s weight to help sort of pull you into it.
If you’ve been doing exercises which promote flexibility it’s probably those working, rather than just the weight loss!