The 18 unit em John mentions is from the metal type days, and it was strictly to do with the widths of the characters. The shapes of the characters were not constrained by any sort of unit grid the way they are in digital fonts.
I have a studio at home, in a repurposed bedroom. I fantasize about having my studio somewhere else sometimes, to make the line between work and not-work less blurry. I did that for a while back in the eighties, sharing a space with an illustrator (who unfortunately was a fan of working while listening to speed metal at maximum volume--we ended up avoiding being in the office at the same time). There are lots of interesting buildings in walking distance from my home. But in the end I can't give up the convenience (or the commute) of working at home. I've done it so long now it's hard to imagine doing otherwise. I've become accustomed to the blurriness.
One advantage to giving the modified font a different name: Both the standard version and the modified version can be installed at the same time. It might seem advantageous to keep the name the same to avoid having to update older documents, but if the modifications to the font are such that they would cause document reflow, it will necessitate updating older documents anyway. And you won't have the option to allow the old documents remain as they were.
In the first example, I think it was done for reasons of formal unity (echoing the curve of the S). I think it's actually okay because, even though it curves "the wrong way", the general orientation (NE/SW with the thicker part at the top) is correct.
In the second example, here again it seems to have been done for formal unity (notice the repetition of the same NW/SE angle throughout the design). This one is less successful and not very well drawn. The whole scheme here feels a bit naïve and the "backwards" apostrophe doesn't help. (See also Cutting Edge Logos.)