I'm almost positive they rewrite everything possible, and this leads to some of these issues too. You can't assume that all of the features from upstream are i

I'm almost positive they rewrite everything possible, and this leads to some of these issues too. You can't assume that all of the features from upstream are in whatever they put in RouterOS. For example, OpenVPN UDP support was finally added to the stable stream this year after 10 years of asking about it.