I turn with the sleeping bag and bivvy bag from the left side to the right and back. (Sleeping mat under the bivvy bag.)
Nevertheless I prefere a wider fit.
The Snugpak Special Forces sleeping bags 1 and 2 and SF bivvy bag are constructed to wear also military boots in it if necessary. There is enough space although they have a mummy shape.
I think Carinthia Tropen too but surely Defence 4 and 6 have a similar cut, I think they are even wider than Snugpak SF bags. A soldier simply needs to leave the boots somewhere in frosty weather and Tropen and Defence 4 are standard issue in a lot of armies, the Austrian and German army for example.
I have seen pretty weird civil sleeping bags also a few decades ago. But if you are right and they become tighter and tighter the reason could be that we have an "ultralight trekking" wave because most European clients work in offices and simply became pretty weak and otherwise people nowadays seem to buy in internet shops, looking at the weight, instead of trying it on in a real shop.
Sended in the last minute before people leave for holydays the stuff is sold and the clients seem to be glad with the product.
But if you want a European made factory new quality sleeping bag with polyester filling you need to buy a Snugpak, Carinthia or Norwegian Isbjorn anyway if you don't try to get one of the few little last French makers.
Who is interested in a quality product gets offered a wide fit too.
May be that a few American mountaineering down bag makers have a rather tight fit although that's quality stuff without any doubt. In dry cold conditions and in steep terrain that might be sensible.
My equipment is comfortable to use and comfortable to carry. I don't need to shorten the handle of my toothbrush.
Nevertheless I can carry it all without any problems because nowadays also very practical equipment became very very light.