Edit. Only occurs when the player is within close proximity and "viewable" by the creeper.
It seems the creeper must be able to "see" the player, before it makes impact.
When the player is separated from the creeper with glass, the creeper always meets it's natural demise, no matter the proximity.
Vincent watson
MCPE-13360
About a year.
Update: a freeze corrupted my world rendering it unable to be opened.
I recorded the seed number, then started building in the same place. It took about 20 minutes of building to start doing it again.
Seed number: 976766941
recorded the seed number, used it to recreate the same world, and then started building in the same place
Same issue. Android 6.0 Huawei p9
Edit. Only occurs when the player is within close proximity and "viewable" by the creeper.
It seems the creeper must be able to "see" the player, before it makes impact.
When the player is separated from the creeper with glass, the creeper always meets it's natural demise, no matter the proximity.