There is a lot of weirdness lurking in the default user agent stylesheet…especially in Safari: https://blog.jim-nielsen.com/2021/things-i-learned-reading-w...
Browser vendors put a lot of surprising, and very poorly documented, defaults into user agent stylesheets, and they can trip you up at the most basic level, and the styling is poorly exposed in most web inspector tooling.
I ran into a nasty one with Safari’s date picker—had to go down a lot of rabbit holes to figure out I needed to finesse the `::-webkit-date-and-time-value` CSS to get an input field styled correctly.