Architects are obligated to protect the health, welfare and safety of a building's occupants, so it is absolutely necessary that the architect have construction knowledge. Anyone who designs a building without any construction knowledge is an artist or a designer; they are not an architect. An architect is held responsible for the conception, execution, and successful completion of a building.
It is necessary to note, however, that a building beyond a rudimentary structure is too much for just one architect to take on or to fully understand all by themselves. Sometimes there are gaps in knowledge, and it takes collaboration with other architects and engineers to safely and successfully execute a design through to its completion.