Not Agree. In HTML (and everywhere) one it is checkedby default. That's why it is radio button.
A radio button or option button is a graphical control element that allows the user to choose only one of a predefinedset of mutually exclusive options. The singular property of a radio button makes it distinct from a checkbox, which allows more than one (or no) item to be selected and for the unselected state to be restored. You have checkbox buttons with radio button functionality
No, it's not a radio button, because you can uncheck all of them. No "Start playback" and no "Resume playback". With radio buttons, you must choose one or another, one must be always checked. This way, we'll need to add a third option "Do nothing". But it's three options - we have two and that's better.
If it were radio buttons, you won't be able to uncheck all. Radio buttons mean one must be checked. In the current setup you can uncheck all. So it's totally different. Checking both does not make sense - you either start playback (from the beginning) or resume it from where it was left off.