If the teaching approach is phenomenon-led then this implies an almost zen-like approach to waves:
see this here – that's not the wave. At the moment this seems to be more-or-less the approach adopted, but with not enough zen, leading to conflation of the phenomena and the theoretical construct. In other work supporting the development of teaching approaches, for example in electric circuits, in introducing descriptions with forces, and pre-eminiently in refocussing the teaching of energy, the preservation of this separation between the lived-in world (particularly tangible experiences and noticed phenomena) and elaborated theoretical descriptions has proved crucial: I suspect that the introductory teaching of waves (remaining, as is usually done pre-16, where algebraic fluency is limited).
A second approach, developed here, is more theoretically-grounded. I think this approach could reap dividends in that teachers will be able to be clearer about the intended outcomes and how these relate to the depiction of a wave to support children’s reasoning. Central to this is to maintain the separation of influence and stuff.