I totally agree with the premise that while technical knowledge is crucial, it shouldn't be the determining factor of whether someone is a Senior Engineer. What is also important is the ability to communicate effectively and mentor other developers.
* More emotionally mature
* More pragmatic
* More business aware
* More recruitment aware
* Better at whatever process you are running
* More security aware
* More performance aware
But more than all of this, ideally there would be an objective progression ladder to ensure they have actually done all of these things not just assume they have because they worked somewhere for 10 years and was called "Senior"