Office 2003 can absolutely open docx and xlsx and pptx files. It is annoying because it usually opens those in read-only mode, and then you need to "save as" to do your modifications. But it works fine otherwise.
“View” unfortunately isn’t the same as “Open and edit”, and in business you need to do the latter. Otherwise we’d be 100% libreoffice from the start. Yep, that’s the moat.
It's been a while, but I think what they're saying is that you have to "save as" in order to be allowed to edit. Office 2003 thinks of the compressed versions as export formats rather than internal formats.
> I think what they're saying is that you have to "save as" in order to be allowed to edit.
The issue is that roundtripping between Office 2007+ and Office 2003 is unreliable and will often result in corrupted files.
Using Office 2003 (with Compatibility Pack add-on to open xlsx and docx) is ok for isolated work but can be unreliable for collaborative back & forth editing depending on what features are used. E.g. cell colors used in Excel 2007 xlsx get corrupted in Excel 2003 xls.
It's a completely different format. Iirc .doc files are basically implementation defined files and consist of c-structs dumped to disk. .docx is a properly specified format of compressed xml.
It's not "C structs dumped to disk". It's https://en.wikipedia.org/wiki/COM_Structured_Storage, which is basically a filesystem-in-a-file. And it has been documented for a long time, ever since Microsoft was forced to write docs for Office file formats because of antitrust:
