Earlier quoted context omitted.
> MagicLinks are a mobile nightmare. Mobile email clients use their own browser and cookie jar which consume the session cookie you're trying to put into the user's main browser. It might be howling into the void but the conclusion I reach from this is that "Mobile email clients are a nightmare". Generally speaking, embedded browsers in mobile apps are a terrible idea and break user expectations in multiple ways.
On the flip side, I find that opening links in isolated sessions very valuable, if not just because I don't want links sent by others to affect the Algorithm's perception of me. 80% of the time, I want to be a blank slate when interacting with in-app browsers.
Meanwhile if the stupid app decides to hijack the link and use in-app browser, you can't do that. And IAB typically means you can't have app and browser in parallel and switch between them from app launcher, which would be sometimes useful. Slack does that, and it's annoying. But at least you can right click> copy URL and open it manually in preferred browser.