It's possible the volume was defaulted at 40% since it was originally....in any case its already been changed for future releases.
But you had troubler reading the font on PC?
Can I ask where it became problematic, since you can change the dialogue font I have to assume it was the preference screen...but I'm running it on my PC at 4K with and without HDR enabled....and frankly I don't have the best vision for small text--I don't have any issues.