That's not his main complaint at all. His complaint is that C#/.NET inhibits him from building abstractions natural to his problem. He gives three good examples of this, obviously drawn from real experience working on real problems. He also gives good examples of the kind of workarounds one is forced into when blocked by a language or library from growing one's own program in a sensible way.
I'll add that, in my experience, most claims about programming that talk about "enforcing" are rooted in theories or processes about programming that bear little relation to what hackers actually do.
That's one way of interpreting it. But it does seem that what he felt was natural was to override methods marked as "do not override" and access members marked "private" or "protected".
Does your experience include creating a public binary API and shipping multiple versions of it? Just asking.
I'll add that, in my experience, most claims about programming that talk about "enforcing" are rooted in theories or processes about programming that bear little relation to what hackers actually do.