Yeah, I understand your confusion, but those conditions are definitely necessary conditions.
Obviously, we can't assume that 'if' will always be followed by a sufficient condition.
What about 'only if?' Well, that's definitely not a sufficient indicator.
Similarly, in this case, you're tipped off by the words 'requirements' and 'must.'
And even the start of the sentence, 'A scientific theory is...'
Analogous to 'People who score 120 on the LSAT are... <insert necessary condition>.'
-- Both sufficient conditions.
I hope that makes sense.