Your rules lawyer "friend" is wrong. The question has been officially answered on March 16, 2009 (at 1:08 p.m.) in the FAQ section over at the game publisher's website, see here:
Hans im Glück-Editor wrote:
Bei der Endabrechnung zählen nur die "richtigen" Werkzeuge. Also keine in irgendeiner Weise auf Karten abgebildete. Max. die 12 Stück auf dem eigenen Tableau.
In case you or your friend don't speak German too well, run the above text through some translating software or trust me in that it means:
When performing the final scoring, only the "real" tools count. So never count any tools that are pictured on the civilization cards. The maximum attainable value is 12 from the tools on your own sheet.