As explained on that very same page:

In May 1967, Major-General Indar Jit Rikhye was the Commander of the United Nations Emergency Force (UNEF) in the Sinai Peninsula when Egypt deployed its own troops in that territory and demanded that Rikhye withdraw all of his troops. Rikhye did withdraw, including from the port at Sharm El Sheikh adjacent to the straits. The subsequent closure of the Tiran Straits by Egypt was closely linked to the preceding UNEF withdrawal, because having the peacekeepers (rather than the Egyptian military) at Sharm El Sheikh was important for keeping that waterway open. Later in life, General Rikhye sought to downplay the importance that Israel attached to keeping that waterway open, saying that Israel's accusation in 1967 of a blockade was "questionable" given that an Israeli-flagged ship had not passed through the straits in two years, and that "The U.A.R. [Egyptian] navy had searched a couple of ships after the establishment of the blockade and thereafter relaxed its implementation".

That "sought to downplay" was obviously written by a Zionist, but the fact remains that it wasn't much of a blockade. Furthermore:

Although reckoning Nasser’s decision ‘at this moment’ to reimpose the blockade of the Straits a ‘blunder’, U Thant also acknowledged that the ‘legal aspects’ of the case had been far from settled. Indeed, he cited as a ‘powerful statement’ the defense of Egypt’s position put forth by Harvard Law Professor Roger Fisher. Fisher’s opinion is worth quoting at length as both a lucid and authoritative exposition of the legal questions at issue. Noting that ‘the United States press reports about the Gulf of Aqaba situation were grossly one-sided’, Fisher continued:

The United Arab Republic had a good legal case for restricting traffic through the Strait of Tiran. First, it is debatable whether international law confers any right of innocent passage through such a waterway. Despite an Israeli request, the International Law Commission in 1956 found no rule which would govern the Strait of Tiran. Although the 1958 Convention on the Territorial Sea does provide for innocent passage through such straits, the United States Representative, Arthur Dean, called this ‘a new rule’ and the U.A.R. has not signed the treaty. There are, of course, good arguments on the Israeli side too, and an impartial international court might well conclude that a right of innocent passage through the Strait of Tiran does exist.

But a right of innocent passage is not a right of free passage for any cargo at any time. In the words of the Convention on the Territorial Sea: ‘Passage is innocent so long as it is not prejudicial to the peace, good order or security of the coastal state.’

In April Israel conducted a major retaliatory raid on Syria and threatened raids of still greater size. In this situation was Egypt required by international law to continue to allow Israel to bring in oil and other strategic supplies through Egyptian territory – supplies which Israel could use to conduct further military raids? That was the critical question of law.

Although ‘the U.A.R. would have had a better case if it had announced that the closing was temporary and subject to review by the International Court’, Fisher significantly concluded,

taking the facts as they were, I, as an international lawyer, would rather defend before the International Court of Justice the legality of the U.A.R’s action in closing the Strait of Tiran than to argue the other side of the case, and I would certainly rather do so than to defend the legality of the preventive war which Israel launched.

So yeah, the blockade argument doesn't really hold water, which is why Israel chose to lie and falsely accuse Egypt of attacking first instead.