It really comes down to differences in the way people believe Kobo should support PDFs. Kobo is 100% correct when it says it fully supports PDFs. If you load a PDF, a Kobo will show you the page exactly as it is specified in the PDF file.
Of course, showing a Letter size page on a 6" (or 5" if you use a Mini) diagonal screen is going to be virtually unreadable. (I say virtually because I can do it with some of my gaming PDFs.)
However, I don't consider this case to be Kobo being misleading. As numerous others have stated, PDFs specify how a page is to be shown. Kobo supports the file format, therefore it shows the page as specified.
Perhaps it would be nice if Kobo attempted to reflow and resize the text. However, given the nature of my PDF books, I would absolutely hate it, as I have no doubt whatsoever that the layout would be completely messed up.
This is not a case of a company being false with consumers. The company is doing exactly what it claims to in the case of PDFs. That there is a small segment of consumers who feel they should be doing more (ie going the extra mile) does not make the company's claim any less true.