Fender paints the cavity with shielding paint and foils the pickguard for shielding on the American Standard, Elite, etc. type guitars I’ve had. Remember that shielding doesn’t really do anything for 60 cycle hum, more for RF and other extraneous noises. However, looking at a Strat, it’s typically wired with non shielded wire throughout, maybe the output jack wire is shielded. Compare to a Les Paul where the pickup, switch, output and tone wires all use shielded wire usually, so it’s definitely a good idea to shield a Strat.