One explanation is to look at the "spun triangulation" givingSnapPy gives to the Weeks manifold. This is composed of two ideal tetrahedra with volumes ~0.83828404504 and ~0.10442331774 adding to the familiar ~0.94270736278.
On the other hand, the given triangulation ofSnapPy gives to the complement of the $5_2$ knot consists of three ideal tetrahedra, all with volume ~0.94270736278. We
We can check that all of thethese various volumes agree by solving the various gluing equations (ensuring (a) that there is no rotation or shearing about edges and ensuring(b) that the cusps are correctly (in)complete).