This is not entirely fair - there are loads of very functional independent Matrix client implementations today already (Element, FluffyChat, Nheko, Hydrogen, Fractal-next, Neochat etc), and a growing number of independent server impls too (Synapse, Dendrite, Conduit, Polyjuice…).

It’s true to compare Matrix with WHATWG though - we used the model of WHATWG’s pragmatism as a direct inspiration for Matrix as an implementation-first approach, where we’d then write an open governance spec (having proven it worked) as per https://spec.matrix.org and eventually merge it into an established standards body like W3C or IETF when stable.