That is correct.
Video can only be cut per frame
Audio on the otherhand can be but to 1/48000 of a second.
As Ann points out, Video can only be edited on a Frame-accurate basis - no partial Frames.
Depending on your Frame-Rate, you can get to 1/24, 1/25 or 1/30 of a Second. The human mind, ears and eyes will most likely not be able to tell, that you were a few 1/48,000 th of a second off.
Yes, audio can be adjusted within 1/100 frame, but that's usually for a sound effects on a different audio track. Do what Bill said to get it within 1/30 of a second. Did you zoon in on your timeline to reveal each frame?
In case its helpful and you dont already know.
To move a clip in 1 frame increments ;
Select clip then ALT > or ALT < ( alt-arrows)
5 frame increments ALT-SHIFT > etc
The Audio CAN be adjusted in increments equal to the Sample Rate, if one changes the TimeCode to Audio Units, but that will not be the same as cutting Video in less-than-Frame increments, which is what it sounds as though the OP is requesting.
Right, that's what I said. If he adjusted the audio within increments greater than 1/30 of a second (if that's his frame rate) to match the light burst, it would also shift the rest of the audio track out of sync from the video that it is paired with.