Understanding can be used as an adjective rather than a verbal noun, to mean that, aye, which is why I think they have now adopted the simple present as the translation. Bear in mind, though, even in English "Una is understanding" can still mean literally that; E.G. "Una is understanding what it means to be poor, now she has lost her job."
Yes, and no. I think in most cases it's fine, because it teaches you what you are really saying, and this kind of idiom is more common in Scottish English, than, say American, at least in the west. It doesn't work with "understanding" because of the specific idiom in English.