Counter: in-app browser is a separate cookie file, so e.g. for X, Nostr, whatever you don’t start collecting shit tracking cookies from sites you open (like MSM links) that then hang around for ages in your system browser, they’re sandboxed separately
counter-counter: If you are a poweruser probably you know how to manage your browser and your cookie in it, but you have near zero-control over in-app browser (they mostly work on the webview package on android, a chrome-lite browser and you need to obtain root and skills (or grapheneos) to harden and modify it.
*literally in my propic on lineageos phone hardening firefox from fdroid*
Fair - though on iOS ofc there’s a lot less control, wiping Safari periodically is a pain