This still doesn't allow you to get your pkg from the entitlement page so you would already need to have the entitlement/ dlc pkg
Also some DLC require extra data files such as DJ Max Respect. The game includes some of the DLC data with the update but you still need the entitlement package with the extra data or it will be unusable.
In that video at the timestamp you can see the dlc shows up in game and till I install the exdata pkg can the dlc cant be used. It will just soft lock the system as a type of DRM protection. If you guys are familiar with the DJ Max series they were notorious for their odd drm protection and their PSP games would do crazy things like flip the screen or jumble notes.
Your case was a lucky one because the data was included within the game, not all games are that gracious.