But read Jabba's statement carefully. You are correct that, for any hypothesis, we can attain a probability vis-à-vis some event. Where it is less correct is under the auspices of the false dilemma. Jabba denotes the hypotheses in play as H and ~H, which ostensibly covers the universe. Because P(H) + P(~H) = 1 is a simple law of probability (and, for some data E, P(H|E) + P(~H|E) = 1), Jabba wants to compute one and then infer the other. This is what everyone does when trying to sneak a false dilemma past his critics. The problem in Jabba's argument is that -- depending on the day -- H is a singular hypothesis and ~H is the disjunction of all other hypotheses, or ~H is the singular hypothesis and H the disjunction of all else.
One day, H is "we are mortal" and ~H is "we are immortal," but then Jabba's test for P(E|H) involves only one select theory -- scientific materialism. It does not, as it should, include all the theories that aren't materialism but don't also lead to immortality.
Other days, H is strictly materialism and ~H is everything else; Jabba purposely keeps his set of options broad because he isn't willing to nail down in exactly what way we might be immortal so that no particular hypothesis has to pass any sort of test. He considers it a strength of his argument that it includes Christian resurrection, Buddhist reincarnation, etc. That set is a disjunction. In some cases the hypotheses in it contradict each other. In the vast remnant of probability Jabba says results from subtracting 1- P(H|E), there lurks an resolved horde of possible hypotheses, not all of which mean immortality. Remember, if H is the singular hypothesis of scientific materialism then hypotheses that contradict scientific materialism but do not result in immortality live in ~H. Therefore Jabba cannot argue that ~H is composed only of all the different ways in which we can be immortal, that P(~H|E) is meaningful toward immortality because of that, and thus that P(~H|E) represents any probability regarding immortality. At best he'd have shown that materialism is improbable among all the ways in which we cannot be immortal. (Jabba tried to soften his argument by saying he would only prove immaterialism, not immortality.)
To fully fix the probability of immortality against materialism, he has to choose one or more hypotheses (I denote them K, L,...) out of ~H -- from among the ones that do result in immortality -- and compute P(K|E), P(L|E) and so forth and show that one of them is markedly more probable than P(H|E). By "the complementary hypothesis" in Jabba's statement, he means (by his notation) everything that isn't materialism, but really (by his words) immortality. This is the equivocation that everyone sees but him.