To me, “ethically sourced” should refer to a statement or claim of compliance with one’s own sense of ethics in regard to the wages/payments earned by the people who extract the material sold by the people who pay them to do so. In other words, I believe that this is about one’s sense of adherence to the ideal of fair pay.
I highly value the opportunity to acquire pieces of material that I trust come from businesses that can reasonably ensure me that the companies that the material is bought from does not pay their miners less than minimum wage as employees or extort them to extract it. So, I prioritise this in my considerations for where I will purchase pieces from.
Acknowledging that it is inappropriate and unprofessional to request the contact details of the sources of the material I am interested in — for me to confirm this for myself, I reasonably take the word of the people I buy it from. As long as I can either look them in the eye, if we are in person, or discuss this with them digitally to determine myself if they are trustable enough for me to feel comfortable and confident in my purchase.