Yes I clicked but didn't notice the Greek overlay. It's neat. I imagine that it can be useful for math, if you're not using something like LaTeX or Emacs already. I even have something similar in my custom layout, although it seldom gets any use. That does not make it any better for programming, nor for typing in Portuguese (or even Greek).
Look, I think it's great that this thing exists and grateful that you mentioned it. I may even suggest it to some of the French-speaking juniors I work with.
It does not, however, address the issues of the person you were replying to. And I know because I'm in a similar position to them.