edge-cache-tag header needed and x-akamai-cache-tag-error

Problem/Motivation

On the settings page you can enable/disable "Enable Edge-Cache-Tag Header". I'm just curious if enabling it is needed? For example, if I disable it, do the cache tags still get sent to Akamai through the x-drupal-cache-tags header directive? And can cache tags still be purged correctly? Just trying to understand here.

On another note, on several of pages I see the following header:

x-akamai-cache-tag-error: TAGSCNT paragraph_14571

What is "TAGSCNT"? Why is there this tag error? Would it cause the page from being cached at the Akamai level?