Is it possible to see the counterpart sign (nimitta) with eyes open?
The proof of the pudding is in the eating, no matter how many books are written about the pudding. Once eaten there can be no mistake about it.

As a samatha meditator, both the signs exist for both types of meditation and which still appear when the eyes are open if they are vivid.

Having said that I've quiet a few  fellow  meditators who do not see the signs but continue to develop Jhanas using feeling.