All chains' elite lines have granted me a free after-6PM cancel for one reason or another over the years. It required a phone call, usually my explaining some unusual circumstance that impacted my travels (weather, etc.), and a response that it was a "courtesy" as a thank you for my loyalty.

I don't doubt that it still works for Plats/Diamonds in the "new" world where same-day is the new 6PM.

If it were a systematic ability to cancel same-day from the app without explanation, that'd be a Plat benefit that would be highly interesting to me.