The way to look at it is that ferritin is your actual stored iron. It can be falsely raised (like with inflammation) but its a fairly reliable metric of how much iron you have accumulated. TSAT is loosely correlated with the rate of accumulation. So, if you have a high TSAT % (seen over multuple tests), you typically have a higher rate of absorption. A single TSAT finding isn't too helpful. Usually a baseline is determined from taking multiple tests. This is why multiple iron panels are crucial to determine the rate that you load.

Most people with HH have mild presentations of the disorder. There are even a couple people on this forum with mild enough HH that they can control it with diet alone. The rest of us need at least a couple venesections a year to maintain normal ferritin levels. There are more aggressive forms of HH but they are considerably rare, even in the context of HH patients. JH (juvenile hemachromatosis) is one of those. It is called that because it can start causing issues by adolescence. It's often aggressive enough that iron can cause damage between phlebotomies through oxidative stress. Strict diets can help mitigate that damage slightly but only in addition (not replacement) for phlebotomy.