Probably this question could sound like why is everyone telling a «docx/xlsx/pptx» formats is undocumented, but it is a bit vague.
I’m just wonder: today I am occasionally found an article at MSDN saying that the «docx/xlsx/pptx» are documented of 2010 year. I am not use Office documents very much, but often hear of others that e.g. «pptx» presentation often displayed wrong in either of MS Office or LO. The arguments I heard so far told that these formats isn’t documented, i.e. its support done with reverse-engineering. But today I found it is wrong, so I am curious:
what is the real problem with these formats?