The typical way a chip effort in a non-chip company works is that the "design" is the RTL (e.g. SystemVerilog that defines the behavior of the chip) and then this is handed off to a third-party "design house" (such as Broadcom) that turns that code into a real image of a chip, which is called a GDS (basically you can think of this as a very big layer by layer photoshop file) that can actually be sent to a fab. This is called "backend design", in contrast to the "frontend design" (the RTL itself).

As another commenter said, Broadcom is very experienced with backend design (as well as the supply chain management, testing, etc. that comes after the chip is taped out) and so this can't be regarded as a "first chip". Richard Ho (the head of hardware at OpenAI) is also extremely experienced and used to be the head of the Google TPU effort -- where he actually worked with Broadcom in a similar tapeout already. So yes, this is not a "first design"!