Bah-
If you have an AMEL ticket it is legal for you to fly it. And it is legal for you to log it. Even if you are logging dual received you can still log PIC as you are already rated in the aircraft. Now if you are logging PIC time on that aircraft and it isn't dual given, you had better be able to talk about it and know whats going on. If you don't know Jack about turbine engines or systems, then I wouldn't log it as such. If you are logging dual received and logging it as PIC, it is legit flight training, regardless of what seat you are sitting in. Go a head, log it, use it, its fine. This is of course dependent on the fact that the other guy is a CFI.

A certain company's requirements may or may not allow you to ride right seat. Certain operations may or may not allow you to ride right seat. If it is 135 PAX, i don't think that you can be in the right seat. But for some reason, if you found someone with a King Air 200 that was out turning jet A into noise under part 91 and they were a CFI, then sure, there is no problem.

Minimums are minimums, and as you spend more and more time in the industry, you will find that some make sense and some don't, but they are what they are. Also remember that minimum time and competitive time are different things.