Question about RF layout seen in application note (Texas Instruments AN043)
Yes of course the 90 degree angle will cause reflections. Anything that isn't a proper transmission line of the right impedance will.

Question is, how much will it reflect and maybe it is low enough. Many times a design might not be perfect but that doesn't mean it's not good enough. I guess in this case the designers wanted flexibility so they placed some pads to place components. And this happened to be the result.