You are somewhat conflating Android's additional "custom tab" API and traditional webviews. To some extent both of them can be used for similar purposes (I need

You are somewhat conflating Android's additional "custom tab" API and traditional webviews. To some extent both of them can be used for similar purposes (I need to display some web content in my app), but only the former allows the user to choose any arbitrary browser that supports that API [1], whereas the latter always uses an app-specfic browser profile and is always powered by Chrome/Blink. It's up to the app developer to choose which of the two implementations to use. [1] Though some apps still used to (or still do?) hard-code Chrome there.