Faxon barrels are NOT dimpled from the factory. The end user would choose the style of gas block and then install it depending on the instructions.
Some barrel manufactures will also void warranty if you dimple the barrel yourself , some will honor warranty if dimpled by a certified gunsmith.
If you use a faxon gas block they do not have to have the dimples because the gasblock they supply bite down on the barrel. Weird but that's what I got was their barrel and their gas block and did some research and found the answers on Faxon's website. Their answer to why they don't dimple their barrels is weird, because it would leave bare metal that would corrode but the gas block would do the exact same thing they don't wan't to happen when it bites down to the metal!
Mine was not dimpled but I like clamp on gas blocks so I didn't need it.