How does the no tip aspect work? Does it mean no tip is required, but is optional... So you open yourself up to the risk of some angry delivery person complaini

How does the no tip aspect work? Does it mean no tip is required, but is optional... So you open yourself up to the risk of some angry delivery person complaining or exacting revenge on your items during the next delivery? Ideally I would like it to be "no tip possible" meaning even if I wanted to tip, I can't.