I hardly think PHK is ADT at all. There are often good engineering reasons to rewrite software. I think Joel's point is that it is more often undertaken for wrong reasons.
There's the software that works, he gets the money to find the bugs and fix them, he decides to write from the scratch something that certainly isn't the replacement of the existing software except for some specific users. That is very ADT, exactly to JWZ's definition:
"This is, I think, the most common way for my bug reports to open source software projects to ever become closed. I report bugs; they go unread for a year, sometimes two; and then (surprise!) that module is rewritten from scratch -- and the new maintainer can't be bothered to check whether his new version has actually solved any of the known problems that existed in the previous version."
He got the money to look for the bugs and to fix them (hard). He instead goes to make the fully new undiscoverd bugs in fully new (his own) code (easy).
