why InterpMotion constructor does not computeVelocity

[MahooX]

hello, I am new here and I read FCL source code recently.
I'm confused about the following code ( in interp_motion-inl.h ,line 120)

template <typename S>
InterpMotion<S>::InterpMotion(
    const Transform3<S>& tf1_, const Transform3<S>& tf2_, const Vector3<S>& O)
  : MotionBase<S>(), tf1(tf1_), tf2(tf2_), tf(tf1), reference_p(O)
{
  // Do nothing
}

why we do nothing in this constructor? Hence, we get undefined angular_vel and linear_vel , which may be wrong.
I find that all other constructors in class InterpMotion will use computeVelocity() to initialize angular_vel and linear_vel.
Is it a Bug?