By my standards it is not but I always buy aftermarket stiffness
The bar is so thin (aero if you put it that way) that even in 38cm lowest they could offer, it bends too much. I do not have the means to do a scientific test but I can provide a video?

.   @Vincent57 I was planning to get this frame set, but without handlebars and seatpost. As you have the bike in flesh, do you think a regular integrated cockpit would work with the steerertube? And is the seatpost the same as ostro vam 2.? I was looking at some aftermarket seatpost instead of the one that tantan provide. Do you haopen to know what width are the axles and what pitch is used for the thread. Thank you for taking the time to reply.