Not true. There is an adage that the government can force you to produce the key to a lock, but not the combination to a safe.

It just so happens that, today, the government can compel you to perform a physical gesture that, by proxy, happens to be used as a key on a device that normally accepts a combination. If it's been 48 hours since your finger was last applied to the Touch ID sensor on an iPhone, that "key" doesn't work any more. So, until the fingerprint is accepted by the courts as a "combination" (effectively, that's how the "common man" sees it, and which the courts treat as testimony-by-proxy) rather than a physical gesture (not testimony at all, and currently easily compelled), the only defense one has (if using Touch ID) is to stall for 48 hours.