I think there was a copy paste error. I didn't write the quote you're responding to.
That's strange. Fixed now.
How is Flensburg City doing in terms of size and economy? If it's diminished we could make a case for the Free City status to be abolished.
Flourishing as a tax shelter.
Are the charters in question available? Do they mention the geographical specification? Or is it tradition that is bring argued?
Dieter IV granted the City of Flensburg the title of a free city without bothering to change the legal status of the County of Flensburg, back when he was both Emperor and Elector Count of Stirland. So all the arguments are based around what 'city' really means.
Dieter didn't care because he got paid either way, but once the Elector Count of Stirland and the Emperor stopped being the same person, things got complicated.