This is a known problem with ksh and ksh93. Given that, I am not sure there is much IBM could do. I would tend to think that the problem would have to be fixed in the ksh code itself, which, of course, IBM doesn't maintain; they are a mere licensee.
Only if IBM put pressure on the maintainer would they fix the problem, and I am not sure IBM would consider this a large enough problem to expend that much effort.