mw13: Why do Chazal tell us to believe it? Who cares? For what purpose? If not that we should make use of it for the correct purposes (not study for its own sake but to further our own Avodas Hashem).
The implication that you derive i.e. believe it but only second-hand and not first-hand even if true is not the main point of the Maamar Chazal.
And anyway it’s not true at all. How exactly do you learn Chochma ‘second-hand’? Are you telling me the Rambam learnt his medical knowledge second-hand with no non-Jewish sources? How then? A series of lectures through a bas-kol? And Chovos Halevovos and other seforim quote extensively from non-Jewish sources. The Rambam also praised the Chochma of Aristotle.
The poshut pshat in this maamar is ‘believe it’, i.e. don’t dismiss it, don’t say Goyim know nothing – they do. Therefore obviously we should make use of it for the right purposes.