faraday cages aren't reflective
First of all, faraday cages aren't reflective (and they are also effective only at certain wavelengths depending on the grid spacing). Any incoming EM on the right frequency will induce small currents in the faraday cage and so not penetrate it.
Unless it has an unshielded external pocket then your phone will not work when inside your suit (or they are lying and it has no effect at all on microwave transmissions).
As protection from lighting it's likely to make things worse not better, the entire wire bit will melt and probably set your suit on fire, plus it might increase your likelihood of being hit in the first place, especially if your trouser hems drag on the ground.