You Can Speak Lashon Kodesh Without Speaking Hebrew
In Parshas Vayigash we find the posuk, "Behold! Your eyes see of my brother Binyamin, that it is my mouth that is speaking to you." (Bereishis 45:12)
Rashi comments that the phrase "that it is my mouth that is speaking to you" refers to the fact that Yosef HaTzaddik spoke to his brothers b'lashon kodesh - in Hebrew.
The Degel Machaneh Ephraim interpreted Rashi's translation of lashon kadosh literally as "holy tongue". The Degel taught that the phrase "that it is my mouth that is speaking to you" means that the brother's understood that it was indeed their brother Yosef speaking to them because Yosef's speech was holy and that his mouth and tongue were free from blemish. Lashon kadosh did not refer to the fact that Yosef spoke in Hebrew, but that his speech was pure, clear, and refined.
Simply put, the Degel taught that one did not need speak Hebrew in order to speak lashon kodesh.