Ice neither forms nor melts at block light level 10

Ice is unable to form or melt at light level 10, this seems to be an off by 1.

Simple tests:

1. /fillbiome ~-20 ~-5 ~-20 ~20 ~10 ~20 snowy_plains
   /fill ~-16 ~-1 ~-16 ~16 ~-1 ~16 glass
   /fill ~-16 ~ ~-16 ~16 ~ ~16 glowstone
   /fill ~-15 ~ ~-15 ~15 ~ ~15 water
   /fill ~-10 ~ ~-10 ~10 ~ ~10 ice
   /weather rain

   → The ice does not form 1 block further than the fill command, no matter how long you wait

2. (from same position as the other commands) /fill ~-11 ~ ~-11 ~11 ~ ~11 ice
   → The ice spawned in by the command does not melt, no matter how long you wait