I have the same problem. Events are entered on the google calendar(s) show up on my Iphone Calendar, but any events created in the Calendar on the iPhone never show up on the Google Calendar.
So it seems that the IOS7 Calendar App is not "syncing" just downloading -- the events only flow one way.
Does it have anything to do with Push vs. Fetch?
I hope there is help for this. I sure cannot find it.