I messed around a bit and found it annoyingly rigid. In reality I would have already established clear communication and rapport with both the ic and the vp.

When we setup our sprint goals we would have built in time to handle random requests aannddd I would have kept in good grace with the vp so that he knows were on the same team even if I say no to the request.

Also, how I respond depends on why the vp decided to backchannel me. If they did because they didnt care about our teams goals (and only theirs) then I might need to escalate to their management to set clear boundaries. If they did so because in the past I forgot about their requests, then I probably need to not forget about their requests.

If they are clearly not looking out for our shared interest (or that of the company) and instead only worried about themselves, maybe slightly narcissistic then Im going to respond in a different tone than if they made a genuine mistake.

Interesting! I haven't come across any teams communicating to sales on sprint goals. ofcourse this could be an early stage startup but that's exactly my point as well. I provide heuristics and guidelines and not a playbook. The final decision will depend on multiple contexts like - your org, stage of the product, org culture, nature of your sales VP and yours, revenue, and a lot more. This is why it is subjective and not deterministic.