IMO, the issue is not very relevant.
In principle, nothing prevent to formulate "complex" hypothesis addressing multiple facts.
See William Whewell about confirmation :
“our hypotheses ought to foretell phenomena which have not yet been observed” (Novum Organon Renovatum, 1858); second, that they should “explain and determine cases of a kind different from those which were contemplated in the formation” of those hypotheses (1858); and third that hypotheses must “become more coherent” over time (1858).
Hypotheses ought to foretell phenomena, “at least all phenomena of the same kind,” Whewell explained. Whewell’s point here is simply that since our hypotheses are in universal form, a true hypothesis will cover all particular instances of the rule, including past, present, and future cases. But he also makes the stronger claim that successful predictions of unknown facts provide greater confirmatory value than explanations of already-known facts. Thus he held the historical claim that “new evidence” is more valuable than “old evidence.”
The modern approach to the logic of confirmation is known as the Hypothetico-Deductive method :
In its simplest form, the idea is that a theory, or more specifically a sentence of that theory which expresses some hypothesis, is confirmed by its true consequences.
Carl Hempel’s description of the method illustrated by the case of Semmelweiss’ inferential procedures in establishing the cause of childbed fever has been presented as a key account of Hypothetico-Deductive method.
Hempel described Semmelsweiss’ procedure as examining various hypotheses that would answer the question about the cause of childbed fever. Some hypotheses conflicted with observable facts and could be rejected as false immediately. Others needed to be tested experimentally by deducing which observable events should follow if the hypothesis were true (what Hempel called the test implications of the hypothesis), then conducting an experiment and observing whether or not the test implications occurred. If the experiment showed the test implication to be false, the hypothesis could be rejected. On the other hand, if the experiment showed the test implications to be true, this did not prove the hypothesis true.
In conclusion, in order to be useful, the method must be applied to as much "simpler" hypothesis as we can, in order to be able to test it against facts.