Congress may submit a proposed constitutional amendment to the states, if the proposed amendment language is approved by a two-thirds vote of both houses. Congress must call a convention for proposing amendments upon application of the legislatures of two-thirds of the states (i.e., 34 of 50 states).
For example, while the legislative ( Congress ) has the power to create law, the executive (president) can veto any legislation; an act that can be overridden by Congress. The president nominates judges to the nation's highest judiciary authority (Supreme Court), but Congress must approve those nominees.
The FRCP 26(a)(2)(B) is a requirement for the expert witness. If the expert fails to include this, then there is a high chance that the testimony can be thrown out.