This is a carryover of the FAT32 file system. FAT32 has a maximum file size of just under 4GB. Even though your card may be formatted using the exFAT file system (which does not have this limit), DJI drones still limit the individual file size to 4GB.
In your video editor, if you place the two files one after the other, you should not notice that the footage comes from two separate files. The final footage should look seamless.
Of course, if you reduced your video resolution, your entire mission may fit into one file provided that it is less than 4GB.