I totally agree with you. I especially think this is counter productive advice:

> Many programs which are correct when viewed at Level 2 are not correct when viewed at Level 3, because they rely on behavior which is not guaranteed to hold in all future versions.

Some level of modularization/abstraction perhaps just keep the system clean, or maybe assist mocking for tests. Maybe even to prepare for some likely changes down the line, but absolutely not "guaranteed to hold in all future versions."