Classification Is Optional for Type 1 Applications But Recommended
For Type 1 devices, classification is optional. In other words, knowledge of the actual power rating of a given PD is not completely essential. But we have just realized it helps a great deal, and should be implemented even for Type 1 devices (it is not optional for Type 2 devices, unless they want to pretend they are Type 1 devices and can be configured to do so by the user).
If the PSE knows power requirements via classification, it can then try to reserve the right amount of power for each classified PD, ensuring its uninterrupted operation, and also ensuring that as many other PDs/ports as possible can be powered up later if desired, with any remaining (surplus) power.