Old execute syntax still works in command blocks that were placed before 1.19.50 and have not been updated by a player interaction

As Shown In the video, the command block runes the old command in new version with no syntax error

How to reproduce

1. Create a world on a version with the command not changed
2. Put the full command in a command block in that world (something that works and does not give a syntax error
3. Update to the last version
4. Open that world

Expected results

The command block you put gives a syntax error

Results

The command block works just fine