There is another situation I can think of. The FAA have a definition of "performing the duties of PIC". This is quite useful in a situation similar to yours, whereby say a multi-engine CPL wannabe pilot needs to build hrs as PIC (for say the ME commercial certificate which requires 10 hrs of ME PIC time). This might also apply if someone say wanted to do a ME PPL without SE privileges, to enable the to PPL to "solo").
The FAA sensibly realised that no one in their right mind would rent a non-ME qualified pilot a twin to build these hours solo, so they allow a safety pilot / FI to be in the aeroplane, yet the sole manipulator to still log PIC.