OED3(?) seems to have bought into something like that:

DRAFT ADDITIONS JUNE 2007

charet, n.

* Chiefly N. Amer. (orig. Archit.). A period of intense (group) work, typically undertaken in order to meet a deadline. Also: a collaborative workshop focusing on a particular problem or project; (Town Planning) a public meeting or conference devoted to discussion of a proposed community building project.
[Probably originally with reference to the former custom among French architecture students of using a cart to carry their work on the day of an exhibition: see Trésor de la Langue Française s.v. charrette.]