First, different materials reflect different wavelengths at different rates. Copper, for example, is the most reflective material for the 10.6um wavelength of our CO2 laser. Aluminum may as well be wood for as little as it reflects.
Second - anyone who’s played with focus height knows there is a very small region where the beam can be effective. Any reflection is not going to be focused to the point of causing damage. If it was that easy to effectively manipulate the beam, they wouldn’t be using precise optical and mechanical components to do it…
Edit: or what evansd2 said!