Before we go any further we would like to confirm if this adapter is the original one installed by factory.
preinstalled was a Intel® Dual Band Wireless-AC 7265, which got replaced by a Dell Technican with the 17265. Also the LCD Backcover and WLAN-Antenna got replaced by the correct one for WiGig functionality.
According to Dell, the E5550 is now equipped with the same Hardware as a Out-Of-The-Box Wigig capable E5550.
The only thing i did not try so far is a complete reinstallation of the Operating System, which i hoped to get around by some software troubleshooting.
But still, the Dual Band Wireless-AC Card displayed in the device manager is confusing me.
By the way... are there Ubuntu/Linux Drivers for Wigig? So i may be able to test the Wigig functionality with a Live-OS before reinstalling completely.
In this particular case, we recommend that you contact Dell* for support regarding this issue as Intel does not support integration which is when the original wireless adapter is replaced by another one. Please check this link for further information: Regulatory Information Regarding Hardware Installation or Upgrade for...
You also may find more information on how to use Intel® WiGig technology by accessing this other link: Frequently Asked Questions About WiGig for Network and I O and also here: Intel® Tri-Band Wireless-AC 17265
As for your question whether it is normal to show in device manager as the Intel® Dual Band Wireless-AC 7265 the answer is yes, it will show like that for the Wi-Fi as for WiGig it will show as Intel® Dual Tri-Band Wireless-AC 17265.