This bypasses the Taiko Music Pass (approx $5/month or $50/year). The developers (Bandai Namco) rely on DLC/subscription revenue. If you enjoy the game, consider buying official DLC or the pass — especially if you play online.
In the custom firmware (CFW) community, an NSP update exclusive often refers to modded integration. Because the game has anti-piracy checks for the Music Pass, specific "update exclusive" patches have been released that trick the game into thinking you have an active subscription. This allows access to the 500+ song library without monthly fees. This is technically exclusive to users who apply the specific update NSP hash (Title ID: 0100A0017F5A6000), which is not available to vanilla Switch owners. taiko no tatsujin rhythm festival nspupdate exclusive
For a legitimate or modified Switch console, the update process is designed to ensure the game runs correctly. This bypasses the Taiko Music Pass (approx $5/month