172,
Instrument time is not required for the private pilot certificate. Flight by reference to instruments, as required by 61.109(a)(3) is NOT instrument training. Therefore, an instructor certificate with an instrument rating ("CFII") is NOT required. For the purposes of meeting this requirement, a regular old CFI will do the trick.
For the purposes of meeting the instrument training requirements of the commercial pilot certificate as specified under 61.129(a)(3)(i), a CFII is required (technically a CFI-IA, for airplanes). The following quote from the AFS-640 FAQ section addresses this topic. It's authored by the man who wrote 14 CFR 61, Mr. Allen Pinkston.
QUESTION: §61.129(c)(3)(i) is the rule that requires instrument training for a commercial pilot certificate with a helicopter rating and the rule states “10 hours of instrument training in an aircraft” Does this instrument training have to be given by a CFII?
ANSWER: Yes and the CFII must be for the category and class of aircraft that the training is being given in. For example, if the training is being given in an airplane, then the CFII would have to hold an instrument-airplane rating on his or her flight instructor. If the training is being given in a helicopter, then the CFII would have to hold an instrument-helicopter rating on his or her flight instructor certificate.
172, you also asked about instruction provided in a simulator or flight training device. If that instruction is required instrument instruction, then yes, it must be given by the holder of a flight instructor certificate with an instrument rating, or a ground instructor certificate with an instrument rating. This means either CFII, or IGI.
You may not buy the legal interpretations, but that's a little like saying you don't buy the law. There you have it; take it up with the Administrator, because a legal interpretation represents the administrator, is legally binding, and fully defensible in administrative court.