There are other instances where both pilots in a required two-pilot crew may log PIC time under FAR 61.51 and 135.
Examples: A type rated pilot receiving instruction from a company flight instructor (also obviously type rated). Both may log PIC time.
A non-type rated pilot (not designated as the aircraft commander (P-1)) who is the sole manipulator of the controls on a non-passenger leg under FAR 135. Both may log PIC time.
The FARs do not follow the JARs.