Maybe, maybe not. Keep in mind that opcodes are the lowest-level part of the programming stack. They're literally just integers transmitted on the system bus. So if you've got, for example, 35 operations that you're actually trying to implement, you need 2^n^ ≥ 35 or n = 6 signal lines in your bus to transmit it. But since 2^6^ = 64, that means it's possible to put another 29 values on that 6-bit bus, with completely undefined behavior unless you go out of your way to handle them in the instruction decoder (increasing the size and therefore cost of your silicon, which is very undesirable in an embedded chip that sells for less than $1).

It is not at all implausible for one of those undefined instructions to just happen to do something that an attacker would find useful, by sheer coincidence.

Probably why Android and apps are constantly asking me to turn on Bluetooth when I dont want or need it.

Not that this chip is in my phone, but it begins to seem like a pattern.

i gather that's why they're referring to the discovery as a 'backdoor'