35mm film (Full Frame) equivalent is very commonly used in photography. 30mm provides objectively more information than 1X, 2X, 3X, 100X. As long as you use the equivalent, you can compare focal lengths across any camera/sensor/lens platform. Yes, the fact that we don't always use that equivalent is just as annoying to me.
Do we know for sure what the "main lens" on the 15 is going to be? Without that information, 3X is useless, while 72mm is objectively useful. 72mm is a great focal length for upper torso portraits or a picture of your pet. Most people probably don't have a clue what 3X even means- most probably assume it's something to do with making something 3X bigger in the frame or looking 3X closer. They just know that bigger number = better, yay marketing. It's nearly as bad as the megapixel race.
This is a good example of why we need objective measurements for these things. This doesn't even make sense. The number of pixels has absolutely nothing to do with focal length or zoom.