My university recently required all professors to attest that they do not consult nor are employed for more than one day per week. This statement is required to ensure the professors are engaged in research or educational activities.
Curious if that is pretty standard in other universities?
This is standard in the US and is more or less required to comply with US federal laws that require evaluation of potential conflicts of interest for people working on federal money. Since money is fungible and every institution gets federal money, that can potentially apply to anyone.
From what I understand of regulatory compliance in general, the government tends to give pretty broad leeway for how exactly institutions comply with this sort of regulation, though they'll also issue more specific guidance from time to time. Institutions tend to copy each other with how they comply so that they can defend their systems if ever challenged. That means that your institution may change exactly how they implement policy even when laws stay the same.
Some further reading (certainly not exhaustive):
https://www.ecfr.gov/current/title-42/chapter-I/subchapter-D/part-50/subpart-F
https://www.ecfr.gov/current/title-45/subtitle-A/subchapter-A/part-94
https://grants.nih.gov/grants/policy/coi/index.htm
Typically, if you have potential financial conflicts of interest, the institution will work with you to develop a plan to deconflict those interests, which can include additional oversight but may also include banning you from certain activities. For example, professors who receive money from pharmaceutical companies for research may be banned from making any patient decisions or being a responsible physician for anyone receiving drugs made by that company or their competitors. There could also be less severe restrictions like merely requiring disclosure or more severe restrictions like ending an employment with the university.
As an addendum, because this seems to come up every time "conflict of interest" is mentioned here, note that "conflict of interest" literally means that interests exist that are in conflict. You have conflict of interest whether or not your behavior with respect to those conflicts is in any way unethical. A conflict just means a conflict. If your child is a student in your class, there is a conflict between fair evaluation of students (an interest of the institution and all of their instructing staff) and success/future of your child (hopefully an interest of every parent). If you receive money for consulting, there is a conflict between your interest in working for whoever you consult for and your interest as a neutral academic. Conflicts are in the interests, not the behavior. Universities maintain integrity by mitigating the appearance or potential influence of conflicts of interest, not merely by punishing behavior demonstrated to be unethical. There is a danger of falling into the trap of not reporting conflicts of interest and therefore failing an ethical duty to report those conflicts when someone judges their own behavior with respect to those conflicts to be ethical. The whole point is that the person with the conflict is not the appropriate person to make those decisions.
In addition to @BryanKrause's accurate description of the "conflict of interest" aspect, there is indeed the aspect of not wanting faculty to put lots of energy into outside activities... rather than their teaching, research, and service on behalf of the university. (My perspective is U.S. R1 places...)
