So I read that article and I am slightly confused by what the conclusion is supposed to be. Especially with respect to the design choices made for permanent vs. temporary tracks.
My perspective is that the permanent tracks have to be suitable to support a variety of types of events. Including amateur (or even lesser pro) events in which hard walls with limited run off would be unacceptable. For example here in the US, it would likely be difficult from a liability perspective if the track was less safe than it could be. Also, (speculation on my part) is that those running circuits are more likely to want something like long run-off areas vs impact absorption devices due to cost (i.e. is cheaper for "Joe Amateur" to slow down and get stuck in a sand trap than to have him destroy an expensive one time use barrier.
I take what Tilke says to be that they don't have to worry about that "as much" for temporary circuits that are effectively geared toward a single event per year (or weekend of events). So temporary circuits can be made more challenging (aka dangerous).
As to F1 requiring the "highest safety rating", I assume that means FIA 1 license tracks. Clearly if Monaco is able to get a "1" without extensive use of "run off", then "run off" is not a hard requirement (as you might think given what we see in new purpose built "1" tracks). I mean Monaco has runoff in some strategic places, but for the most part it is just hard barriers everywhere.
I would love to know how the FIA track license/grading system works, but I have read that what differentiates a "1" vs. a "2" is as much other ancillary things (various facility stuff such as medical center, lighting, equipment, etc.) as it is pure track safety.
Regarding how FIA rates circuits, the best link I can find is here...
https://www.fia.com/circuit-safety
Which does not explicitly say how they define the boundaries between licenses/grades. I suspect it is a highly subjective evaluation so they probably don't want hard rules defined on paper. Again... Monaco being a prime example of if hard rules existed, they would likely require being bent to ensure the race continues. Nobody wants to be responsible for creating the rule that stops racing at Monaco.
Richard