You are creating a word inference /and differential, that isn't there, in a practicality sense, and in a communication sense, as well. When someone says, say, 'I believe in Jesus', this does not infer that they do not have 'knowledge', of the validity of their adherence' they might think they do, or, they might they don't, it isn't what is being communicated, (solely), in that expression, or statement.
Aside from that, your idea encounters the problem of 'valid evidence'. This is a /necessarily/ ie by reality, a subjective thing. We have different measurements, or parameters, for what constitutes valid evidence. One person might consider vaid evidence to be simply what they are taught, or read in a holy book, etc., another might consider valid evidence to imply that said deity must tattoo a mermaid on their shoulder, in order to be considered real, etc. It's entirely personal, and subjective.