That’s the current font stack as far as I can see:
-apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif
The screenshots in the first post are very small and of poor quality. My guess would be that you use Windows and you are now seeing Segoe, which is a default on Windows. The earlier version might have used Arial, which is still in the font stack, but comes after Segoe, so it’s not used if Segoe is present. That’s how these font stacks work. If no web font is forced, than you get ANY of the fonts in the list. Nothing wrong with that, but you can easily override that in the custom.css if you want a preference for Arial for example.