Whether they're improvements or notor not you consider a design choice is left as an exerciseimprovement is up to the readeryou.
That said, see the Stacks GitHub repoStacks GitHub repo* releases section, and specifically the changelog. https://github.com/StackExchange/Stacks/releasesthe changelog for each release.
In your case, I believe thatThat specific change was made in v2in Stacks release v2.3.0. (It's the onechange labeled Important in purple text)
*Stacks is the design system Stack Exchange uses for the SE network.