Yes, I noticed the 53.0.112 upgrade.
It upgraded the Adobe RMSDK (the rendering engine) to 9.3.1.433
I'm not sure what, if anything, has improved.
Font size steps should be small enough that you get what you want and big enough that you can notice the difference.
Some publishers are very heavy handed with CSS.
I'm sure you've noticed that you open a book from one publisher and suddenly the font size is larger or smaller than what you normally see.
Even on DRM books (without decrypting) you have the "nuclear option".
Unzip the epub, delete all CSS, rezip.
I have a Windows utility called "unduke.exe" which does this in one step.
You can guess which publisher I hate the most.
I don't annotate or care how long to chapter end anyway.