wow this cable is really weird, the dielectric is what looks to be tightly wound plumbers tape. I guess it aids in flex, but wow. Its braid over aluminized mylar over what looks like used car lot ribbons over packed teflon tape over a solid wire. Feels SO dodgy to work on.
I think you can make DIY hardline cable by winding plumber tape over a wire and wrapping it with copper tape or stuffing it in the right diameter plumbing lol, my work bench looks like it got TPed
I believe that kind of dielectric is not super uncommon in highly flexible cables. It is always all a tradeoff between loss, flexibility, repeatability, and cost. Using precision wrapped cores like that could result in a much more flexible cable since they can slide over eachother a bit. Usually during cable design, they take care that the distance between the different wraps is much smaller than the wavelegnth, because otherwise you can get strange notches in the frequency response of the cable. Same is true for wrapped outer conductors using silver-plated foils. They have to control the force during wrapping and the pitch very well to ensure good cable performance. Very high frequency cables tend to start putting the foil wrap length wise, so you put multiple pieces of foil in the length of the cable, and then wrap it with the outer braid to keep it in place. Gives lower loss, higher frequency performance, but at the cost of flexibility and bending life.
Just because it is made that way does not mean it is easy to repair. After all, you can think of coaxial cables as a conductive rod with non-coductive wrapping and then some more conductor. Doesn't mean you can make a 30 GHz coaxial cable with some gardening tools though.
As to the reason why they don't have higher frequency 3.5 mm connectors available for that cable: They usually have a limited set of connector types with specific outer diameters. It might not be make financial sense to make a custom version of a high-frequency 3.5 mm connector for this specific outer diameter, and instead just switch to 2.92 mm instead (which they might also be able to use on other cables that go to say 40 GHz).
Gore, H+S, Amphenol, etc all sell cables with connectors that cannot reach the maximum specified frequency of the cable. EG, Gore 50 GHz phaseflex with 3.5 mm or 2.92 mm connectors, H+S Sucoflex 102 (rated to 46 GHz iirc) with N connectors, etc etc.
It's simply easier to design a cable that is good to 50 GHz, and use it for a number of assemblies from 10->50 GHz, than make a specific cable for each type. Coaxial extrusion dies for these kinds of applications can run in to the tens or even hundreds of thousands of euros to manufacture.