The brake side of the axle is the same as the 142mm axle. We just shortened the freewheel side by 7mm. Result is that you can't use more than a 5-speed freewheel. Otherwise it's pretty much the same geometry
If I had a hubmotor business, this is how I would do it. By making the axle-shoulders "just right" to fit into common bicycle drop-outs (at 135mm), and the torque arms are on the outside of the frame. At that point, these axles will fit a thousand different frame models, and the extra axle length can be easily cut if desired. However, the extra axle length is needed depending on how thick the torque-arms are. If aluminum, they will need to be fairly thick. Axles can be cut, but can't be stretched, so...extra length is the right choice for a vendor.
Its always funny to me when someone who wants a hubmotor that is capable of 3000W-5000W wants to have a lot of gears available...If you want 750W, get a geared hub or mid drive, if you want 1000W-2000W, there are cheaper and lighter DD hubs and mid drives available.
But...once you ride an ebike with 3000W or more? for some builders, that become their minimum standard. If that sounds like you, then...asking for more speeds than two is ridiculous. Use the smallest available single-speed freewheel, and then maybe swap-in a two-chainring BB crankset with a chain tensioner. One gear is the "I want to pedal along in the lower half of the motors power band"...and...the other gear is "something went wrong, and I have to actually pedal home with no power".
Asking for a cassette freehub or anything more than a 3-speed freewheel is something that those low-powered
DD hubmotor owners do. The stock 3000W MXUS DD hubmotor is awesome, and the "turbo" version sold by Kinaye is "awesome plus-1". Barent is just being polite. Take my advice, if you are in the market for a MXUS 3000W Turbo? Feed it a lot of watts, you won't regret it. And...if you're feeding it a lot of watts? you don't need a lot of gears.