Er, but the description of a “well-architected monolith” here is a set of loosely coupled components (with specific criteria for where you at component boundaries) communicating over an external set of message queues, which, while it doesn't have all the features which define a microservice architecture, is itself a widely documented, well-known, older (heavily documented in the 1990s, possibly older) alternative to monoliths. I suppose this is being called a monolith because everything except the message bus is implicitly jammed into a single process rather than each module being in its own process. But, even aside from the modularization being different from a monolith, bringing messaging out of process makes a huge difference compared to even a modularized single-process solution.