I don't mind that people aren't knowledgeable because we all started some place. But some people are so unknowing they don't even have the experience to grasp how much they don't know and some of those people tend to be very aggressively outspoken on subjects where their personal knowledge is zero and everything they know is gleaned from internet surfing. That thread about factory brass being intentionally made so it couldn't be reloaded was a perfect example. That thread was full of silliness and couldn't be taken seriously by most, but the unfortunate possibility is that another unknowing newb will read it and be lead astray like you were.
You are taking about a different thread but there is lots of evidence that some commercial factory ammo is made with cheaper lower quality brass - when the manufacturers can get away with it. Typically they are using brass with less than than the 30% zinc that is called-for in cartridge brass. They seem to do this especially for older calibers that aren't running at modern, higher pressures - like 303 British. I'm not the only source of evidence. Lots of useful comments from multiple people in that thread. No need to worry about some imaginary unknowing newb being lead astray.