This is still an issue in 1.6.1 of bedrock. Creepers will not spawn in 1.8 height areas
I am on Bedrock v1.2.13 and can say that this seems to still be an issue as of May2018. I have trading hall and iron farm with a bunch of villagers lined up in 1x1 cells. They all have glass over them and the walkway in front has half slabs of cobble above. BUT I came in to find that 4 sequentially in line villagers in their 1x1 cells had been turned into witches. The only way I can think this happened is that lightning came through the ceiling of slabs or glass+slabs and struck them.
this has been a persistent issue for bedrock for a few versions now... at this point there is insane lag spike when playing on 1.10 and on Realms for me. Sometimes have to wait like 30secs to open. I hope this is a top priority issue for Mojang. (Yay "Bug"rock!)