This is misleading. SpaceX pushed Falcon 9 so much that it actually reached the targeted Falcon Heavy payload years before that. Many early Falcon Heavy costumers launched on Falcon 9.
There was very little market for Falcon Heavy and the main costumer was DoD and their launch was scheduled for pretty late.
The simply didn't work on Falcon Heavy until Falcon 9 was at the end of its evolution and they had figured out re-usability. However the end result was more then double as powerful then the version announced in 2013.
This is not to say that what SpaceX is doing isn't incredible. But I get frustrated when articles like this take the promises of things like "<$10m per launch, and up to thousands of launches per year" as an absolute truth.
Edit: Had the original contracted launch date for the STP-2 mission wrong
There have been some preliminary studies on spacecraft that could take advantage of a Starship launch capability, but we currently can't transport a spacecraft that large over the road. It would most likely have to be transported by ship from the manufacturing facility to the launch site. Additionally, new test facilities like thermal vacuum chambers, acoustic cells and anechoic chambers would likely have to be created to handle the large spacecraft that a Starship could enable. And NASA is not going to make that investment until there is a higher probability of the Starship succeeding.
Those in the industry are pretty cautious about Elon's promises. Back in 2011, SpaceX advertised that the first Falcon heavy flight was going to be in 2013 [0], but the demo flight didn't occur until 2018, with the first launch of an actual payload in 2019.
[0] https://www.reuters.com/article/space-business-rocket-idUSN0...