Initially noticed while experimenting with the experimental snapshots 1 for the 1.19 but applies to 1.18.1 and the 1.18.2 pre-release 2

likely a game logic bug the clip from 1.18.2 pre-release actually had 4 flowing water blocks removed, source blocks are also effected, I set up a command block out side the box in the Minecraft 1.18.2 Pre-release 2 blue skull bug.mp4 and that fills air blocks with bedrock the removal happens when the blue skulls explode.