Ok let’s talk about observations. Let’s say we walk into a room and there’s a glass of water sitting under a faucet and that faucet is dripping 0.05 ml per second. We measure how much water is in the glass and there’s 240 ml in it. So 240 ml multiplied by 0.05 gives us 4,800 seconds. 4,800 seconds gives us 80 minutes or exactly 1 hour and 20 minutes. So according to our observation we can conclude that the glass has been sitting under the leaking faucet for 1 hour and 20 minutes. Then as we look around the room we find a camera pointed at the faucet and we check the video footage and find that someone came in 5 minutes ago, got the glass out of the cabinet, got a drink of water then placed it under the faucet. Well our calculations were correct and our math was correct, but our assumption on how much water was in the glass to begin with was incorrect and that completely thru our observational data right out the window. So we can know the rate at which radioactive isotopes decay and we can measure them correctly and calculate how long ago it was that a particular material didn’t have any isotopic decay but what we can’t know is how much isotopic decay the material had when it was created 6,000 years ago. To say it had zero isotopic decay at some point is an assumption just like assuming the glass of water was empty when it was placed under the leaking faucet. We don’t know what these materials were exposed to during the creation process or how it would’ve affected them, so we can’t actually say that we know how much isotopic decay they should’ve had 6,000 years ago. You can make the same exact argument with radioactive accumulation or C14 decay which is all over the place since C14 levels fluctuate like crazy.
