Well, the wording is ambiguous. I thought just as you, but my friend convinced me to the possibility of drawing from the deck directly. I wished the authors would answer.
When drawing Artifact you MAY draw from an artifact card from dig site - it is an option. Also using string rules as Figures cards use from triggers word "INSTEAD" should be added to this rule.
And of course Beta rules are not finished and maybe not final, so maybe final rulebook clearer. Reulebook will have to be written very carefully because , rules for drawing from 6 types of sources (5 types of decks and dig sites) are VERY complicated