I thought T refers to overgrown top management and a long tail of managers managing other managers. And one guy at the bottom doing all the typing.
Scrum master, Business Analyst, misc devs and QA contribute marginally and hope that one developer who groks the entire thing gets something done.
And then there's the "lone genius" who is doing everything in order to prevent anyone else from contributing.
Developers add cleverness until only themselves grok the accidental complexity, QA and BA's develop the actually useful bits on the side, the developers quit to implement more Cloud at the next startup.
Introducing the Q shaped model...
T shapes are used also for building teams so you think about an overlap of people who understand at a high level what others are doing but still emphasize the individual specialization of subject matter experts. It's like Tetris but for teams.
“a T-shaped organization is both good at the management of its existing operations, as well as being good at the strategy and innovation needed for a healthy future.”
Some might say that this just describes a ‘viable’ organisation.
Being more practical about it, Gordon Moore’s Escape Velocity would be a good modern read.