To be more precise, this covers the current implementation in Safari 12.1. I will have a generic article over on https://developers.google.com/web/updates/ once it launches more broadly.
I checked, 2.27:1 for the background color to the input background color. For text contrast, that’d be not enough, for separating the input field from the background it seems OK. The more important text contrast with the input field background is great at 7.27:1.
The tragedy here is that the Vibration API was actually fully implemented, but then got removed again. If you have a compelling use case, consider commenting on the bug and ask Apple to re-considerate their decision.