afaik , pptp does not push route(s) to the client. It just uses classfull routing based on IP address given.
For a 192.168.x.x , the client only sends /24 through the tunnel
For a 10.x.x.x. address, the client send entire 10.x.x.x/8 through tunnel.
On client, checkbox is present, to send all traffic through tunnel. (Windows , hidden under IP4 tab "use GW on remote network." )