It technically does indeed matter, because "then" means a totally different thing in that sentence, but using "then" in that way would be an odd enough way to construct that sentence that it's blindingly obvious that they meant "than".
What reasonable interpretation of the sentence is there if "then" is applied literally? I can only find validity using "than", and therefore the use of "then" doesn't matter as the author's intent isn't lost. That said, carrying the assumption that it does matter forward, how are you certain "then" isn't the correct interpretation of the author's intent?