Dissolve Bone does nothing to two adjacent bones?

Hey Folks, using Blender 2.92.0 here with a humanoid mesh imported from MakeHuman using the standard .mhx2 import plugin. This brings in a fully pre-built armature with it.

There are some unnecessary bones in the mix, such as the lower legs and upper & lower arms each being split into two bones... which I've decided I should make more anatomically correct for the sake of weight painting, animation, and performance.

The limited data I could find on this points to a simple process of selecting the two bones (in edit mode) then choosing the Delete > Dissolve Bones option to turn them into a single bone still properly chained in relation to their neighbors.

*This doesn't do anything. No result, no blender errors, nothing\*

I've tried re-opening my file.
I've tried doing this first-thing immediately after importing the file.
I can delete either/both of the bones in question, normal delete on the same bones works fine.
The documentation on this feature is missing.
Only search results I found were people explaining how to do it years ago, no mention of any weird requirements that may be interfering with the operation.

Anyone have an idea what I'm missing here?