The original guidance IIRC is to both wear masks and maintain social distance. My interpretation of this was that if you are wearing a mask, not only are you filtering the air you take in, but also out, and even with a cloth mask, you are at the very least reducing the radius of what you are shedding vs being unmasked and talking out loud.
To me this was all null and void if you are sharing a tight enclosed space for any significant period of time- like a restaurant, or even an office. Then you need something like an N95 to get any significant protection.
I understand people's frustration, but I think its important to remember that organizations like the CDC are trying to make a recommendation that balances many factors like convenience/discomfort vs availability of masks, vs what is actually understood about the transmissibility of the virus in its ever changing forms. Even taking that into account, it seems relatively simple to set up experiments that can test the effectiveness of these claims- and why no one has done this is kind of baffling to me- I am guessing these are prevented by ethics concerns where you will have to expose healthy people to the virus.