The chronology doesn't really tell the full story. Hoefler made some stand out typefaces, but many of the commercial successes and culturally iconic fonts were designed by Frere-Jones by himself or in partnership with Hoefler. Gotham is the biggest example, but Whitney, Surveyor, Archer, Vitesse and others were either FJ or collaboration work.

It's quite fair to say that Hoefler would not be in the position he is today without Frere-Jones, and by many accounts, and even how Hoefler presented things in the press, they were a partnership. Even before they started officially working together, Hoefler was consulting Frere-Jones on ideas, such as on Knockout - http://www.nytimes.com/2010/01/11/arts/11iht-design11.html

It's not like Hoefler's foundry was a juggernaut when Frere-Jones began contributing to his work, or even when he joined the company. They had several success stories - but so did FJ prior to that - and both of their largest successes all came when they were working together.

How so? Frere-Jones comes later, but becomes vital to the new state of the business. 15 years together!

See 37signals for another such example: design studio, but oh, software is where we shine, but I need this tech fellow as full partner.

That's not an accurate chronology.