I wouldn't rely on better homes and gardens for construction advice, Roger Cook said not to do it and suggested doing a deck, and the third site said a deck is the best option also.
first, you need to excavate for the patio so you will hit roots.
second, compacting gravel with in the root zone will be detrimental to the tree.
third unless you are using a permeable paver you will take away all water and nutrients that tree was ever going to get.
You possible could get away with encroaching 10-15% of the root zone and not hurting the tree.
Feel free to post pictures of the finished product, I believe there is a forum all ready started.
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