Operators are one of the last places in Blender to use older UI designs that don't fit in
with recent style conventions. Updates for consistency and clarity can greatly improve
the experience here.
Some of the code is also simplified a lot. Some of the older operator UIs were much more
complex (in terms of code) than they needed to be.
|Blend from shape operator|
|Object convert operator|
|New image operator|
Although the diffs look very messy these are very simple, purely visual changes. So I
would propose this change for 2.90. Along with the other updates to UI this would
fit in well (in my opinion).