Hi Sean,
I tried the same in my local setup.
When the operating system is set to “iPhone” then the announcement displays only on iPhone devices.
Please see the images below.
View post on imgur.com
View post on imgur.com
As mentioned in the documentation page, the type of browser, OS is deducted from the user agent string.
You can learn more about user agent string here – https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent
Regarding identifying web view or browser, you need to know the UA string. On the below page, you can find how UA string varies for apps. Similarly you must identify the UA and put that keyword in the visitor condition.
https://gist.github.com/taylorhughes/dae564f63b3d702429a5f37bd22b97b8
Regarding the time taken for the update, the changes are reflected immediately. Make sure you are not looking at the cached page.
Thanks,
Aakash