When in the first main phase of the the active player’s turn the active players says something alone the lines of ‘attack?’ or ‘combat phase’ it indicates that the active player wants to move on to the beginning of combat step, which is within the combat phase, AND is passing priority to the non-active player.

If the non-active player does play spells and abilities, it is assumed that he or she is doing so in the beginning of combat step and not in the first main phase. In these instances where something is played in this step, both players will receive priority at least one more time before the game advances on. If however the non-active player does nothing, then the game moves on and the active player will declare attacking creatures.

This is not just a common shortcut that is accepted by most players, it is an official shortcut that is in the Magic Tournament Rules. You cannot be intentionally unclear about where in the turn structure that the game is in an attempt to gain an advantage.