Indeed, it's a lesson I learnt the hard way and is much like proofreading something you wrote, you don't see the errors as easily as someone else you asked to proofread it usually does (well until you hit Send then you usually see all of them instantly).
The devs did use the software, but used it in such a different way from everyone else that when the devs optimized for their own case, it made the software actively worse for everyone else.