Yes, fonts are 1px larger now. This change was made here:
https://github.com/discourse/discourse/commit/5c09792f79f40b057f5da9a38de71b3ec2d2241d
Generally 16px is the browser default, and this is considered a good starting point for accessibility. Minimum font size? | Accessible Web
If the smaller 15px size is preferred, this can be changed in a theme by adding:
:root {
--base-font-size: 0.938em; // eq. to 15px
--base-font-size-larger: 1.063em; // eq. to 17px
--base-font-size-largest: 1.118em; // eq. to 19px
}