Naming inconsistencies in booktitle fields of BibTeX entries provided by IEEEXplore
In general, the quality of Bibtex entries produced by the IEEE website is low. For instance, they do not properly escape capitals in titles nor diacritics in author names, and they do not identify names and surnames correctly. See for instance the Bibtex for this paper (found searching at random on their website), in which they did two of these mistakes and even forgot some HTML character codes in the title. 

So it does not surprise me at all that there is also this inconsistency. I don't think they even bother checking, they just spew out whatever is in their database as a raw string. They put zero effort in them.