C++11 breaking changes in const-correctness guarantees 13 years ago
The author is a total idiot.
The C++ language is totally unsafe, so when you call third-party code, literally anything can happen.
Just because there might be a convention for "const" methods to be thread-safe doesn't mean that they are actually implemented this way, regardless of what the language spec says.
It's alarming that this guy apparently writes books, hopefully no one reads them.