We have 100% native support for xlsx and xlsm file formats
We have 100% native support for xls file format
We have natiev pdf report generation from xls and xlsx files.
We have 100% native support for previewing and printing xls and xlsx files.
We used to say in that page "Support for chart rendering", because we do support chart rendering in xls, but when xlsx was released we removed that line. We removed it completely, even when we do support chart rendering in xls, because we prefer to err in the safety side and not get people confused.
We always try to make sure docs are up to date, but documentation is huge, and you might find somewhere that it says that "rendering charts is supported" (even if I am not aware of any mention in the current docs), but that would be something written when xls was the only format and we did support it.
And trying to keep up to date a "not implemented" document would be a huge effort. We could have a line in the web page like "ACOT function not supported!" and millions of similar ones, but it would be incredibly hard to list everything that is implemented and that is not.
We prefer to spend this time adding as many features as we can. But realistically there will always be a lot of things not implemented, and many I am not even aware of. Just yesterday I got an email to support removing the green triangles in formulas with errors, and I didn't know that was possible (it wasn't possible in Excel 2003, but it looks like they added support in 2007, and I didn't realize). Hours before that I got a request for FIPS support, and I didn't even know what FIPS was. (and yes, we already added FIPS support and are working in adding "ignoreErrors" API. We implement as much as possible, but a completely new chart engine isn't just something we can implement in a weekend).
As documenting every supported/not supported feature is not feasible, what we do instead is to provide fully functional trials so you can know if the features you need are implemented or not. But if you bought by mistake, please email me at email@example.com
and we will refund you your money. We know we can't satisfy everybody, and we really don't want unhappy customers. If the feature set isn't the one you need, we can try to add the missing features (sadly not in this case because the feature is too big), or give you the money back.