I've done blind compressor shoot-outs where people have preferred ITB to OTB units, where it's commonly accepted that ITB compressors don't do the envelopes right. Isolated tests ultimately have little real-life relevance. Just like that test on GS where most people preferred a Behringer ADA8000 conversion to a Lynx Aurora. It's about the cumulative effect. Whether we are talking about the benefits of using high quality mic preamps, or stacking tracks to see what retains midrange clarity best, it isn't about reducing it to a microcosm and analyzing in microscopic detail. It's about what feels right at the end of the day, and what provides beneficial results on a consistent basis. If you compared directly on most speaker systems a majority of people wouldn't be able to tell tracks recorded through an API 3124+ or an Mbox 3, but nonetheless we use the high quality pres for the entire record, because we know down the track it will matter.
Of course moving a mic 1cm will sound more different to a source tone than making an IR of the same position. That's assuming we are judging the differences on a linear scale. The moved mic will still sound more dynamic than the IR, regardless of being different to the source tone, with probably a highly deviant frequency response.
It isn't about how similar or different the IR sounds to the real cab at first glance - it's about how well it retains that illusion in a full arrangement, after it has had a chain of processing applied to it, and is expected to hold down vital midrange frequencies like rhythm guitar tones in metal generally have to. Once again, if I had found IR-based cabinet simulation satisfactory for this I would never outsource reamps. It costs me and my clients time, and I already have all the amps I would ever want to reamp here into IRs, power amp and all. The clips I posted on the other thread show clear, mix-related results. The IR-based tones always create greater congestion in the midrange frequencies in the finished product. Whether or not people are going to validate this by listening to isolated guitar tone samples is irrelevant.