That link tells you this: > Cross-site documents are always put into a different process, whether the navigation is in the current tab, a new tab, or an iframe

That link tells you this: > Cross-site documents are always put into a different process, whether the navigation is in the current tab, a new tab, or an iframe (i.e., one web page embedded inside another). Note that only a subset of sites are isolated on Android, to reduce overhead.