It's a document error I believe. If you go to the Proset download link here: Download Center it says that it's not compatible with Windows 8.1 32-bit. 64-bit is clearly supported.
Here's the excerpt:
Which file should you download?
If you have Windows 8.1 32-Bit:
DRIVERS ONLY: wireless_16.6.0_De132.exe
Intel PROSet/Wireless WiFi Software (includes Drivers): wireless_16.6.0_e132.exe
Note: The following adapters do not support Windows 8.1 32-Bit:
Intel® Dual Band Wireless-AC 7260
Intel® Dual Band Wireless-N 7260
Intel® Wireless-N 7260
Intel® Dual Band Wireless-AC 3160
Intel® Dual Band Wireless-AC 7260 for Desktop
If you have Windows 8.1 64-Bit:
DRIVERS ONLY: Wireless_16.6.0_De164.exe
Intel PROSet/Wireless WiFi Software (includes Drivers): Wireless_16.6.0_e164.exe
Follow these links for details on the differences between the different download file types, and information on Intel PROSet/Wireless WiFi Software.
The driver version of some products may not update. Learn more about Intel Wireless adapter driver versions.
Thanks, theveterans - that makes sense.