You aren't wrong, but that requires asking the question is this hex value correct? There are mistakes I can see without thinking such as missing semicolons and there are mistakes that require me to mentally tell myself "check this value". I would love to get to the point where my brain notices that I flipped a hex character automatically, but I rarely have the chance to work with bytes and hex values directly.

If I see 345,345,345+123,123,123=578,578,578,578 I probably wouldn't notice that this is incorrect but once I decide to really look at it the three errors are obvious.