>What this means is that you can explain all the intent of your code through the header file and the developer who uses your lib/code never has to look at the actual implementations of the code.

I hate this. If my intellisense isn't providing sufficient info (generated from doc comments), then I need to go look at the implementation. This just adds burden.

Headers are unequivocally a bad design choice, and this is why most of every language past the nineties got rid of them.