does "keepalive 10 60" push anything other to the client?
Yes, see the manual for the commands that are pushed to clients.
(cable unplugged)
When cable is unplaged, the OpenVPN does not see this. A connection error will be detected, when some data will try to send, for example by "keepalive" pings. If there is no "keepalive", only when some other application will try to send something to the OpenVPN server IP only, as when the cable is unplaged, the system will modify routing table and all default traffic will go thru ppp, but OpenVPN will not be aware about this.
You can use "keepalive 10 60" in the client too.