OAR is a relative term here.
If you saw the movie in IMAX, you saw some footage in IMAX Aspect Ration. But what if we're presented with the film as shown for the standard presentation, where the switching between aspect ratios did not occur?
Is that wrong, or is that what was the preferred presentation by the director? Does he actually have a preference?
There are relatively few movies with shifting aspect ratios in the first place and only a small fraction of those get released with shifting ratios for home viewing. The only director I know of who expressed a preference (i.e. insisted) that shifting ratios be released is Nolan. And even then, he only released it that way in Blu-ray (the DVD doesn't have it--perhaps because of limitations of DVD but more likely (speculation) because HDTVs are still not in the majority of homes today (much less so several years ago) and the shifting ratio would look horrible on a standard def TV).
Steven Soderbergh made a film some years ago called The Good German. He intended it as an homage to film noir from the 40s and wanted it released in the old Academy 1.37:1 ratio (almost indistinguishable from the SDTV ratio of 1.33:1). The studio refused and it was released at the cinema in 1.85:1. However, Soderbergh was able to have it released in his preferred ratio for home viewing. Having seen it in each ratio, I prefer the 1:37:1, even though, technically, it isn't OAR if compared to the theatrical release.
The Artist, however, was able to get a 1.37:1 ratio in the theatrical release--perhaps owing to its silent film aspect.