This still happens on v0.15.90 on Galaxy S5 phone. Creeper blew up 3 blocks in front (horizontal) of me as I approached it slowly. I also had a creeper >4 blocks below and 1 block behind me blow up.
I have encountered the same thing, also on a Samsung Galaxy S5 but under MCPE 0.13.1 alpha.
Clarification: I initially tried this with a world originally created under MCPE < 0.12.x with the results mentioned in the OP.
When I create a new world in 0.13.1, still on the Samsung Galaxy S5 I was able to convert more quartz blocks to quartz pillars. Oddly, it allowed me to convert 15 quartz blocks into 15 quartz pillar blocks. The expected behavior was to produce 14 quartz pillar blocks, display the not enough materials message and leave me with 14 quartz pillar blocks and 1 quartz block.
This also happens with my Samsung Galaxy 5 phone (Android version 6.0.1) and MCPE 0.15.90 alpha build 1 version.
From the initial report it sounded like this was thought to only affect mobs from an earlier version, but I had an adult zombie attack at the speed of a baby zombie (possibly a little faster).
Also I noticed that the rabbits no longer run fast when I approach them or hit them. The hop animation plays at the regular (non-running) speed, but the distance they move is the normal wandering distance.