This doesn't make sense to me. Law enforcement has been able to get that information easily for quite some time directly from telephony systems. Timestamps and durations have been a part of phone UIs for quite some time, which to me indicates that it is in fact interesting to more than law enforcement... unless phone manufacturers conspired to display that information to help LEOs when they confiscate phones.
Anyone who cares about state coercion and violence should know phone calls are about the least sensitive way to communicate.