To be clear “schok” and “kalus rosh” are two different, but related, things.
In my understanding “kalus rosh” means “flirtatious talking or behavior.”
In my understanding “schok” means having fun or laughing together in a non-platonic manner.
While I fear that kalus rosh is problem particularly in the post-engagement stage, my primary concern is with the schok that goes on after the first few dates when the couple start trying to have fun together. It seems to me that “having fun together” on a date is by definition schok because the purpose of the fun is to create and bolster a non-platonic relationship (unlike playing ping-pong with your sister-in-law).
What I understood gavra-at-work to be arguing was that “schok” requires something beyond non-platonic, (i.e. something that would lead to a more immediate danger of issurei kares). I am not sure I buy the chiluk (are there any objective activities that are forbidden according to GAW because of schok? Does it all depend on the intent of the parties?).