I feel like there is a bit of ethical hysteresis here.
If you have buttons that are designed to be placebo from the start, I find that unethical.
If you have buttons that work, but have to be disabled due to a change in plans, that strikes me as less problematic (but they should still eventually be removed).
If you have buttons that are designed to be placebo from the start, I find that unethical.
If you have buttons that work, but have to be disabled due to a change in plans, that strikes me as less problematic (but they should still eventually be removed).
So, how you get there matters.