Btw, regardless of the EM radiation, a simple EM shield will solve the problem.
Not really: if your chip has technology that relies on encryption keys built into the chip that are common to all similar chips (ex.: practically all DRM schemes), a hacker can buy his own chip, delid it, extract secrets from his own chip, then use those to hack your system.
If an intelligence agency wants to unlock your phone, it can buy a couple of identical phones, get access to the SoCs, use it them to train their equipment on monitoring key points needed to extract keys from the device or run an offline password search, then use this expertise to unlock your device without busting the maximum tries before self-reset.
The article isn't about remote hacking, it is about how formerly impractical ways of reverse-engineering data out of chips are becoming cheaper and more accurate as chips get smaller and thinner to the point that the die can be back-probed. The article mentions one of the "side-channel" methods being luminescence of semiconductor junctions, you obviously wouldn't be able to exploit that without line-of-sight access to the bare die and cementing the chip to an optical bench.