The ablaze 1 LEDs are polarized. In other words they will only work in certain circuits and are Polarity sensitive. The Ablaze 3 LED are not polarity sensitive. They can work in any polarity circuit and use diodes to "steer" the correct voltage polarity to the LEDs.
So a single Ablaze will usually only work where the base is Negative and the tip is positive.
Take for example a Joker Poker . The circuit for the 1000, 2000, etc lights has the Positive voltage on the lamp base. To turn them on a Negative voltage, Ground, is needed at the lamp tip. So if you put the single Ablaze LED into this circuit it will not work as it expects to see a ground on the base and Positive on the Tip. Putting in a 3 LED Ablaze and it doesn't matter as the built in diodes "steer" the voltages to the LEDs so they will work irregardless of Voltage Polarity.