I have the Jervenbag Exclusive with both liners. The bag w/o liners is constantly in my day sack. I use it for catnapping on day hikes (it's an age thing) and getting out of the wind/weather when on lunch stops. Makes a big difference. Also use it as a "poncho" in poor weather, although if I know loads of rain is due I'll take my cag as well. As a poncho it covers both me and my day sack (35L) easily, including my legs. Also great as groundsheet when on picnics with GF. Have never used the bag with the liners but do use the liners for sitting around in in camp on cool evenings. It's a piece of kit that works well for me.
Do you have by any chance a side by side pic to compare volume when rolled please?