It seems you find LoC as a measure of productivity. This would answer your question as to why the author does not find it makes them more productive. If total output increases, but quality decreases (which in terms of code means more bugs) then has productivity increased or has it stayed the same?

To answer my own question, if you can pump out features faster but turn around and spend more time on bugs than you do previously then your productivity is likely net neutral.

There is a reason LoC as a measure of productivity has been shunned from the industry for many, many years.