Stan,
Encore needs a way for the resume button to know what title to play. This if for a subtitle track, or audio track change. Most likely it's for a main feature.
a Play Movie button is not a professional made disc if the Play Movie button doesn't resume the main feature.
Honestly, it's not confusing if you have ever tried to make a professional DVD/Bluray before. Every client I make a disc will wonder why you the Play movie button doesn't resume after you have started the title.