As posted, there is a new guide.
So I think there is confusion in the thread.
The ones which use the 4 or 5-sided "platform" are the former version. The links above will show the new one as well as the "current" version of the former model, which is still sold as an alternative. The former guide was sold for a long time in basically two incarnations, mainly the difference was the change with the angle setting portion.
Honing guides are like any other tool. There are options galore out there.
The cambered lower assembly is just like described above. The roller itself is curved out to each end, and there is a flat portion in the middle for the ability to still do certain straight edge tools without changing the lower assembly.
Here's a picture of the one I cambered myself early last year:
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I don't think is as cambered as theirs, but the principle is the same. This allows me to hone various curvetures to planes I desire them on, while still being able to accurately control the bevel angle.
I can hone as tight as a LN scrub plane blade, which I believe is a
1.5" radius. Many of my planes have some amount of camber, except thise which are for joint making or refining. Having the cambered attachment is nice, and it does not interfer, as mentioned above, with the microbevel adjustment.
My personal opinion is why should they have an exchange program? DeWalt doesn't and last time I checked, none of the other power or hand tool makers do.
Take care, Mike