It's up to you to consider it,
but between that and the closure of Straits of Tiran by Egypt (which is effectively an act of war) there was no illusion there that war is coming.
Do you think Israel would stay complacent with Straits of Tiran effectively sealed from their shipping by Egypt? That's like having someone putting you on a choke hold while proclaiming no aggressive intent... it's not gonna fool anyone.
And the other thing to consider is this: WHEN did Menachem Begin made those statement? WHAT was the political climate to him at that point? WHO can benefit from his statement and HOW would it help him?
political statements... are made all the time, up and down, left and right like a twisted tree, no one said politic is pleasant or convenient to sort out.
But there are things that are difficult to mask:
1. troops concentration
2. popular sentiment
By late May 1967, the momentum in Egypt and the other arab states was such that even if you somehow brainwash Nasser and made him a pacifist, he would not be able to stop Egypt from starting a war... the preparation was made, the situation was perfect, the arab states sentiment were echoing and supporting it...
there was no stopping then.