Yes, good points. I think (but not sure) that the change from MS Office binary file formats (with their issues of being proprietary, undocumented, etc.) to zipp

Yes, good points. I think (but not sure) that the change from MS Office binary file formats (with their issues of being proprietary, undocumented, etc.) to zipped XML formats (for Word, Excel, Powerpoint, etc.) came at the same time as when they added an "x" to the filename extensions, like changing .doc to .docx, .xls to .xlsx, and so on. This was also probably around the time when there was that big public hoo-ha about MS XML formats vs. Open Office / Open Document formats. I had read some about it at the time, don't remember the full details.