That is not correct.
If you were not the pilot in command or could not log PIC under 14 CFR 61.51, then you would need to either show it as instruction received (with an instructor signature), or SIC, if you were qualified based on the type of operation (the Cheyenne is a single pilot airplane, so the only requirement for a SIC would be based on the type of operations: eg, Part 135....which you couldn't be flying for if you didn't hold a multi engine rating).
You can log the time..but without a legal basis, and that's not a very good idea.
Total time must have a category of time that qualifies to log the time in the first place, and you weren't PIC or rated (and thus can't log PIC as sole manipulator), haven't indicated you were receiving instruction, and weren't SIC in an operation that legally required a SIC. There's no basis to log the time.
Someone told you that you could log time in a multi engine airplane, but not log multi-time? Hopefully that person wasn't an instructor.