Rosettes and Revelations Pt.1: The Holy City - Koen Gheuens and Cary Rapaport

[Koen G]

How so?

Because the evidence so far points towards the custom you refer to gaining popularity in the 2nd half of the 15th century.

it is more important to highlight the external boundary as the internal boundary is marked by other features.

Isn't that exactly the opposite of what your examples show though? The hashing is touching those areas already marked by other features.