[zaphar]

A break the engineer chooses is chosen and is unlikely to interrupt flow. An interruption caused by the tooling is not chosen and is more likely to interrupt flow.

Tooling cruft also increases the startup cost of some tasks. Where the amount of pain you will experience trying to do it may inhibit your desire to dig in.

The author was generalizing he wasn't assuming perfect accuracy. But in an engineering organization the size of Twitter the productivity gains of a dedicated tooling team add up fast. Much faster than you might think.