MSCompatUnicodeTable takes a long time when entering Playmode

I followed the instructions from @lukaszunity posted here:
https://forum.unity.com/threads/example-project-assembly-definition-files.482313/page-3#post-3292894

... in order to debug the >5s delay we experience after script compilation. It turns out that more often than not, the profiler shows up a single class MSCompatUnicodeTable taking an extraordinary amount of time (2.5s), and no other classes/methods. Functions were either HasSpecialWeight() and Category() and the Total % is over 22 million.

Here's an example from the editor profiling:


My question: what should we make of this?
Can we assume that this means the delay we're experiencing is due to Unity internally doing stuff rather than us wasting time with an InitializeOnLoad script?

 

Actually the classes/methods that come up seem totally random:

 

I see ... it's probably related to this:

Skipping profile frame. Receiver can not keep up with the amount of data sent