Tablet: How to pass the current mode during pad initialization ?

I read https://wayland.app/protocols/tablet-unstable-v2#zwp_tablet_pad_group_v2, but I don't see any explanation how we should send the current mode to a client. I think this information must be part of the pad initialization, else the application cannot know the current state when the tablet is initialized. Also, the message zwp_tablet_pad_v2::button(0) is redundant with zwp_tablet_pad_group_v2::mode_switch().