These usages may be equivalent. The latter is what I find troubling. Perhaps I missed an important part of the discussion. I think it is generally agreed that all of the definitions in the SUO must ultimately be grounded in axioms of first-order logic. But it is not clear whether there is any dominant opinion that the use of frames with slots must therefore be avoided.
Frames can be a very useful notation for permitting easy understanding of the concept being defined.
Much of the content of Cyc could be expressed in a frame language. The need in many areas for FOPC and eventually constructs which are arguably higher order drove Cycorp to a more expressive language. I certainly won't argue against simplicity. I'd just suggest that we make use of more complex language features when they afford an advantage in simplicity, compactness, clarity or ease of use. All are valid considerations that must be balanced.