I think you are correct. There is no limit that I've seen that restricts output. I have seen laws in multiple states that limit the number of lights in use while the vehicle is moving (typically 4) now wether these laws are actually enforced and have any teeth? Nah, they're typically "fix it" tickets. You _fix_ the issue, show up in court, have the ticket dropped, pay your court fees on the way out.

It's more akin to revenue generation rather than safety enforcement.