I 'm afraid you're right. Text below is from the manual:
•When the motion picture size is set to [FHD], [HD] or [VGA] in [MP4], you can continuously record a motion picture up to 29 minutes 59 seconds or until the file size reaches 4GB. You can check the recordable time on the screen.–Since the file size becomes larger with [FHD], recording with [FHD] will stop before29 minutes 59 seconds.
•You can continuously record a motion picture with its size set to [4K] in [MP4] without a pause even if the motion picture exceeds 4GB. However, the recorded content has to be played back as multiple files
Second part got me confused. Looked like a smart way of Panasonic to get around the situation. Each new files is the start of a new recording, in effect bypassing the limitation.
Alas not the case.