First the file size limit isn't because of a file system limit. DJI uses the "exFat" file system when formatting the card. The max file size limit under this file system is 16 EB (Exabyte). This limit is imposed by DJI and can be best explained by a GoPro support page as GoPro also breaks up long videos into multiple 4GB files which GoPro calls "Chapters".
From GoPro Support:
Question
How are chapters created with GoPro cameras?
Answer
When taking a video recording, the camera will automatically segment into a new file chapter once it has reached a certain size. These files when put together with editing software will play seamlessly as if they were never chaptered, and when played back from the camera directly will also play through as one continuation.
This chaptering is intentional and there is no way to keep the camera from doing so. Chapters are divided like this so in the event of a jolt or crash that causes a file to become corrupted, only a portion of your video will be effected and not the whole thing. While there is a file recovery feature in the camera, chaptering is a precaution step just in case the feature is unable to fix the video.
Source:
GoPro Camera File Chaptering Information