I don’t see that mentioning anything about covering the headphone jack before the test. As I understand it, being ip65/68 means it’s both, where 65 is “low power spray” and 68 is “immersion”, not that it’s 68 only if some unspecified conditions are applied
Still nothing to support that it’s not actually ip68 rated as advertised.
Perhaps you’re just wrong it this? It’s fine to be wrong sometimes