Sudden change in how format rules (font size, boldness, etc.) affect appearance?

[Kirk_Masden]

This post might be filed under the heading "I can live with this but I'd still like to know what happened."

I noticed a change in the appearance of my app today.  For comparison purposes, I found an old video (left side) and put an analogous current view on the right.

I think the difference between the first two images is particularly pronounced.  It seems to be the case that the effect of format rules is greater than it used to be.  

As I wrote above, I can live with this change but I'd like some confirmation about it.  Anyone else notice a similar change in your app?

[Kirk_Masden]

P.S. Since posting this, I recalled that there was probably a difference in the font size setting between the image in the video and the current view.  Nonetheless, the letters still seem significantly bolder so I'm still curious about what has happened.