Cliff, I appreciate your suggestions but I have to direct you to my initial post where I mentioned that I've been an SCA for numerous site collections. I am very familiar with the basic steps to cut/paste data from Excel into a list in Datasheet view.
Troubleshooting
I further trouble shot this issue by getting my hands on a second windows machine with less restrictive admin settings. Both machines are running Win10 & Internet Explorer 11. On the machine where the issue presented, the Custom Security Level for this zone (Internet Options > Security > Internet > Custom Level, see picture below) is set for me by the sys admins and locked from any edits. This machine cannot cut/paste from an outside source. The other machine I tested has those settings unlocked and the cut/paste feature works as its supposed to from Excel to SharePoint.
Conclusion
If you run into this problem, test your site collection on a wide open Win10 machine where you have full admin rights. In my case, it was the settings in IE11 that were the root cause of this problem. I don't claim to be an IE expert, but after comparing the settings, this was the only difference between the two machines. I hope this information helps stop someone from pulling their hair out due to this frustrating issue in the future!