I guess it depends on your goals. For weight loss benefits I think you're right. But coffee does contain caffeine which has to be metabolized so it apparently interferes with other health benefits of IF, eg autophagy.
Madness, I tell you.
Good luck and have fun with the intermittent fasting :)
Far and wide the best ground advice you can give yourself and others is to work out - that'll do good things to you, even if you can do it a little. Other than that, eat a moderately varied set of foods. Anything further than that is usually just something someone came up with in the shower and that other people thought sounded real good.