Those should be closed systems and don't need to network with other systems and should be safe enough, its when we start networking that it becomes incredibly risky which is what neuralink is intended to do. I don't think the average person understands how many automated attacks are flooding interconnected computers as we speak and you're dropping someone's brain into that and we don't understand the scope of what can be done intentionally or unintentionally, it's not outside the realm of possibility an automated attack trying to rapidly port scan and compromise a neuralink could overwhelm and damage the device and cause brain damage or death.

There are people out there with short-range, wireless pacemakers with no security. Most just provide information you'd expect but some of them are also defibrillators (they can kill). As far as I know none have been harmed in an hacked attack but a hacked brain implant brings to mind more than just killing the owner. We may have an interest as a society in making this illegal because it's not worth the gamble to us for people's actions to be hijacked remotely.