There are no conditional "rules". The numbered conditionals that are often taught to learners of the English language are simply common combinations of verb constructions in the protasis (if-clause) and apodosis (main clause) of conditional sentences.
An alternative way to conceive of conditional sentences is through the semantic lens rather than through the traditional (in EFL teaching) syntactic lens. The Grammar Book An ESL / EFL Teacher's Course (p548) has a Semantic Hierarchy of Conditional Sentence Types. It comprises more than twenty nodes, one of which is Implicit Inference Conditionals, which are a subset of Factual Conditionals.
The sentence you are asking about appears to fulfill the criteria of this conditional type. Here is an extract from The Grammar Book's explanation of Implicit Inference Conditionals.
Factual conditionals that express an implicit inference are different
from generic or habitual factuals in that they express inferences
about specific time-bound relationships. As such, they make use of a
much wider range of tense and aspect markers, and they also occur with
certain modal auxiliaries.
... implicit inference factuals tend to maintain the same tense and
aspect or the same modal in both clauses—even though they make use of
a much wider range of tenses and auxiliary verbs.
In "His arm has grown long indeed," said Gimli, "if he can draw snow down from the north to trouble us here three hundred leagues away" the implicit inference is that his arm has grown long, which is based on the fact that he can draw/has drawn snow down from the north.