Possibly, but such laxity is just one of a multitude...vunribble, Febuary, Wensdy...and so forth. All just part of the ongoing pageant that any language is. We may not like it, but we just have to lump it, I'm afraid.
I wouldn't have thought so. Sixth is hard to say (you have to fit an S sound between the K and the TH) but six isn't. As QM says, things change all the time