ESA50 & corresponding descriptor

The revised WCA Handbook (Final Edition 2011) does have this interesting paragraph in it.It's on Page 9.

Sensory Function
In the 2008 regulations, the activities in this area reflected impairment. Adaptation had not been taken into account in these areas. The review group felt that an individual’s ability to adapt must be taken into account and therefore the activity of vision has changed to the concept of being able to safely navigate. The activities of hearing and speech have been changed to the more functional concept of being able to receive communication and communicate with others.

Does it follow then that the descriptors in Section 8, Getting About Safely, should be concerned with more than just vision?

And whilst I'm on I also read on page 14 (1.5 Overview of the ESA claim process) that:

In most cases, the claimant is sent a form ESA 50 that they are expected to complete. This form gives the claimant the opportunity to provide details of their illnesses, treatment and functional abilities and restrictions. If a claimant has a Mental Function problem there is no compulsion for them to complete this form.

So if you have a mental health problem you don't have to complete the ESA 50?