The NotoSans fonts were included in the bundle to handle a problem with generating PDFs on Macs. The problem was with third-party software. See 1st PDF in session renders incorrectly.
That problem was supposedly resolved, so the fonts were removed. The program is now supposed to use fonts in a specified order. See Change GUI font - #4 by lubos. What @lubos was referring to earlier in this thread was his expectation that you should automatically be using one of the Helvetica fonts, which should include the Greek characters.
You should never go backwards in versions. And the current version is 18.9.48.