I think you are over reaching here. It is clear that Laver was the best player in the world by far in 1967, but he doesn't mean that he could have the four true slam. I had a look at the fields of the 1967 pro slams and it is not so impressive.
To win the french pro, he defeated a certain Mackay in the QF (the tournaments begins here for him), then Stolle, then Gimeno, on wood.
At Wembley pro he defeated Mackay again, Davidson, Rosewall on indoors (which surface I don't know).
At the US Pro he had to play four matches: Olmedo, Ayala, Stolle, Gimeno.
At Wimbledon pro, 3 matches were enough again: Stolle, then Gimeno, then Rosewall.
None of these were played on clay, Rosewall's best surface. So, as we know how many times the ultra dominant player of a year failed to win the calendar slam, I think it is overreaching to consider that he had 97% chance to win it all. A deeper field in each tournament, a tournament to be played on his main rival best surface, it make it harder.