100% that aluminum is flexing, the question is how much matters to OP? A CNC router has far beefier extruded aluminum gantries but still flexes from the weight of the router, although typically less than a mil. My guess would be at least 10-15mil with the aluminum angle.
OP said about 1/16", which would be what? 50 or 60 mil? Honestly, though, it's woodworking. In the right context, like coarse slab flattening, 1/16" might be fine, though I would reckon that the point where fine tuning by other means is not that bad would be closer to 1/32".
