Meandering is part of the direction the river is flowing. When it meanders, it really does flow around the meander.

Real life cartography does simplify details out of the geometry of a feature, but it's not about the origin of the detail; it's about the size. We don't care whether a bend was caused by meandering or not, just about whether it is visually meaningful to include it on a particular map given its size.

An average flow direction over the course of multiple meander cycles is something that might be included in a thematic map about historical river flow, but it wouldn't normally be a consideration in reference maps, and certainly not in navigational ones.