Yeah, it's fun to ridicule government employees, isn't it?
The FAA's published requirements were developed jointly with Boeing and GE, and used terminology in the preamble that came from messages Boeing sent to their operators. This is done to be consistent with manufacturer publications whenever possible. The statement about the results of multiple engine power loss is required by policy and by FAA counsel - the AD must state the unsafe condition, even if it's obvious.
In this case there was a lot of discussion to reach agreement on an appropriate limitation because there is no direct way to detect the ice crystal conditions in advance of being in them, and wind is a factor. This was not an easy issue to positively address without potentially creating a large economic impact.
It would be a mistake to assume the FAA engineering staff is incompetent. Just ask Tim (tdracer).