I was thinking the same thing and wondered how they applied to open barrel crimpers.
At the same time, I bought a bag of 100+ closed barrel butt splice connectors without the the plastic sheathing years ago and have found them to work well in my open barrel crimpers to do a butt splice. They are a tube with a split so I just orient the connector so the crimper pushes the ends down and continues the rolled portion and finishes like an open barrel connector. The typical open barrel type splice connectors I have are a side by side type and make the wire run wider at that point while the repurposed closed barrel connectors these keep things inline. Covered with some heatshrink with the glue and they seem to work well.
Big drawback to that is there isn't a strain relief to it since they don't crimp onto the insulation like a true open barrel connector would. My hope is that the heatshrink works for that some.
Pretty sure there are inline open barrel connectors that would work similarly, but my usual source (Eastern Beaver) does show any.