The sixth trump was originally singular. In French it is L'Amoureux, the lover, not the lovers, and the older image is not a couple at all. A young man stands between two women while a winged archer aims down at the scene from above. Whatever the two women represent, and readings from virtue and vice to mother and bride have been proposed, the card is structurally about a man in the middle of a decision, with an arrow about to be loosed at him.
That structure is not preserved in the deck most modern readers use. The 1909 Rider-Waite-Smith card replaces the triangle with Eden, and Waite disparages the older interpretation explicitly. Once the two women become one woman and the archer becomes the angel Raphael, the card stops being a dilemma and becomes a union, and the modern keyword "the Lovers, harmony, partnership" follows from the new picture rather than from anything older.
Both readings are now current, and the honest position is that they are different cards wearing the same number. A reader working a Marseille deck who reads this card as a choice under pressure is reading the fifteenth-century image correctly. A reader working the Waite deck who reads it as the union of opposites is reading the twentieth-century image correctly. What is not defensible is the common move of asserting the union reading as the card's ancient meaning, since the ancient card shows a man who has not chosen yet and is being shot at while he decides.
There is a further wrinkle worth naming. The winged archer above the older card is usually taken for Cupid, and Cupid's arrows in the Renaissance were not benign; they compelled. A card in which desire is imposed from outside rather than chosen from within is a considerably darker object than the one most modern decks print, and readers working a Marseille pattern often keep that edge.