Agree with Al. Should really stay on ground freq until ready to ask for permission to enter the runway, or unless instructed otherwise. No harm monitoring tower on the other radio as it gives awareness of what's going on in the air. Ground might need to talk to you at any time so you really should stay with them until ready to talk to tower.
Nothing dangerous about being cleared for the option at any stage, controllers know what they are doing, they can change your clearance if they want. If you think something is wrong then ask.