This will happen in most browsers (I’m on Safari 14, macOS 11.2). The popup-blockers in most browsers will allow a popup if it is opened directly because of user input, such as a button click — a fairly simple measure which can be implemented by only allowing certain APIs to work within an event handler, for example.

There are a few Web APIs which work this way — for example, you can’t make a page fullscreen unless you do so in response to user input/interaction [0].

[0]: https://developer.mozilla.org/en-US/docs/Web/API/Element/req...

Popups triggered by a user are considered trusted and are usually allowed

https://developer.mozilla.org/en-US/docs/Web/API/Event/isTru...

That's intentional. Instant popups from clicks can have totally legitimate uses (like logging into sites like Disqus/Paypal etc on external sites).

Delayed popups have very few, if any, legitimate uses.