This is not precisely correct. You are required to disclose the existence of patents you hold, and whether or not you're willing to license them on royalty-free or FRAND terms. You are not required to disclose the patent numbers.
On page 3, where the space for entering patent numbers is, it says they are "desired but not required for options 1 [royalty-free] and 2 [FRAND]; required in ITU for option 3 [refusal to commit to either of those licensing terms]". ISO actually allows you to claim you have patents on a standard, refuse to license them to anyone at any price, and not even tell anyone what the patents are, much less which part of the standard they cover. This has happened to at least one standard that was attempting to be royalty-free.
In general, you can assume the answer to the question, "Does the proponent of this technology have patents covering it?" is yes, for the reasons I outlined in the GP. So in practice the above disclosures provide nearly zero information. They don't help you evaluate alternative designs, because you don't know what you need to change to avoid the patents. You also don't know when one party might have patents on a contribution made by a different party [1]. The disclosure is at the level of the standard as a whole, and not by individual feature.
The disclosures are also not very specific about the actual licensing terms. I've had an expert lawyer who made her career on dealing with patent licensing tell me with a straight face that she had no idea what FRAND means. In some industries, it is common practice to require someone to sign an NDA before you will even tell them what your supposedly "non-discriminatory" terms are.
The actual licensing terms are negotiated well after the standard is complete, by which point it is too late to solve problems by excluding technology.
[1] This is quite common. People read the contributions of others and rush to file something based on the direction they think it is going. That ensures they have patents on the standard regardless of whether or not any of their own contributions make it in.
