Remote buttons can differ from DVD player to DVD player, and functionality can also be altered within the authoring software. I like to think of Play going along with Pause & Stop, as transport controls, and "Enter" being used to active the selected program material. That seems to be the way the virtual remote works within DVD Architect.
Another area where DVD players vary is with the Menu button. Some remotes have a "Top Menu" button, some just have a "Menu" button, and some have both.