What is there to disagree about? That's not the same as watching a directory and processing a file as soon as it exists.

Depending on the size of the package there is a good chance the package could not even be validated and complete in under 5 seconds when run via Agent.

This is not to mention that having an Agent job run a job every 5 seconds would be a foolish thing to do when considering other aspects of the system. The calls Agent makes to msdb would bloat your plan cache to no end with only running a job every 15 seconds