"The team reverse-engineered the proprietary wireless signalling systems used by the implants which revealed flaws in the way data was broadcast."
From this sentence alone, it is entirely obvious: The signals are not encrypted; there is no security to hack. These aren't flaws at all - they are design decisions. The manufacturers have some command protocol that they developed and use; while this may not be publicly documented, it is hardly secret: monitor the signals used, and you can figure it out. This doesn't take a "security researcher", all it takes is a kid with the right radio kit.
People then rush to ask: Why do these devices not secure their signals? It may be that they never thought about it. However, the answer may also be that they want an open interface. Consider: you have a pacemaker and suddenly have a heart problem, and you are taken to the nearest hospital. With a secure interface, how does that hospital get the private key required to talk to your pacemaker? Which is the lesser risk to the patient's health: leaving the interface open, or securing it?