You are talking about two different issues. If the check say "SamZMan and Toyota Direct" Both signers are needed for that instrument. If the check says SamZman, Toyota Direct either may cash it. This is not my opinion, this is banking policy and law. If you don't believe me go to your bank and ask the bank manager.
This is a similar concept when you have an account with multiple signers. If the account say "And" you must have two signers. if it just has "," either party signing will be fine.
Just because you have not had a problem yet, does not mean it is correct to do it that way.