Was this a deliberate choice by Microsoft to steer people away from Google products, or is it something more benign than that?
I expect that if this were the problem, OP wouldn't be mentioning it.
When you attempt to use the right-click menu to copy and paste, you get a clearly-worded message box that tells you that you need to use the keyboard shortcuts, and which keyboard shortcuts to use.
Go make friends with someone who works on Safari, then take them out for drinks. You'll understand why I'm saying what I'm saying. :)
He tells me that Edge is often very quirky in very subtle ways. He's had to spend many, many hours diagnosing, reporting, and working around quirks in Edge. These quirks sometimes get fixed and sometimes do not, but are often not present in Internet Explorer.
That being said, since our JS is generated, it's purely ES5 since it still has to run on IE9. So maybe the weird cases are in the more modern JS parts we don't use.