Two strokes are not simple they only seem simple (sic F.Overmars)
If the reed timing self adjusts what causes that? The throttle? The reeds themselves? The ignition? RPM? My bet is again the pipe(and the throttle). The reeds will not open fully when the throttle is not open fully.
Stand off in non existant on rotary valve engines when on pipe same with piston ports. The common theme is that the PIPE is the over riding influence. I can assure you that a inlet where it uses reeds to start and then swing out of the way once on pipe makes much better HP on the dyno and runs perfectly.
Any simple simulator shows the reeds lifting at BDC as this is the time the pipe is sucking hardest.If the engine wanted more air/fuel at this point why not give it to the engine? The fully open inlet is similar to above the exhaust port starting holes in big bore mxers and perforated rear cone kart pipes. The holes 'disappear' when on pipe,