Having a maxed tier 1 artifact (54 traits) equipped should still display the button while research tomes are in the player's inventory. I'm pretty sure the detection is wonky, as it only shows the button for artifacts that aren't maxed.

This probably is caused by either a GUI issue (not checking for the tomes in the inventory cache while the artifact is maxed) or possibly the research tomes not being counted properly during OnInventoryUpdate events - the latter seems unlikely, though.

This was a different issue altogether and has been fixed with 49b692e