For estate properties, why does the MLS question who signed the listing agreement? Isn’t confirmation of authorized signatories the responsibility of the title company?

REALTORS® have a fiduciary duty to the clients they serve, but the MLS has a fiduciary duty to its participating brokers. The MLS is unable to accept a listing for an estate without documentation evidencing that the person(s) who signed the contract has the sole authority to convey title. This is to assure our cooperating brokers that they may proceed to closing without worrying that the authority of the person who signed the listing contract will be challenged in the eleventh hour.