Hi, thanks for the reminder.
The trouble with LTNs is there are so many of them, with over 100 across the country (mostly in London). Some of these have (multiple) passes or permits, which would flood the available list in Waze. Each of those permits would likely only be used by a small number of users (if at all).
We also see many users not understanding what the passes are for, and adding all of them then wondering why they get routed through restricted areas. So it seems safer to keep the majority of routes going around those neighbourhoods, on the assumption that local residentials know how to get in and out of their areas.
Hope that makes sense.