I don't fully understand why this makes me so angry, but it does. The company you work for has no right to know anything about your personal life. To be expected to disclose things to HR is ridiculous.
And if you read that, you're still asking why HR has any right to know if their executives are in a possible enanglement with a subordinate?
OK, maybe you have a reflexive hate of HR. don't fixate on them. Instead, pretend you were in the shoes of Square's founders or major investors, and you're reading a lawsuit that accuses your COO of sexual harassment, the kind of sexual harassment allegation that can only come from a COO who broke standard operating procedure (I.e. not informing HR of this)
Would you think the investors and partners are more angrier or less angrier than you right now?
A person no matter what level he is at who has a genuine consensual relationship with another employee should not cause the company any issues which HR would need to resolve so I still don't understand the need to declare all such relationships to them.
For what it's worth, in the UK it's perfectly OK to have a secret office romance and such things are not required to be declared. It could be that our cultural differences are the main reason for this difference in opinion.