Magma cubes currently spawn in lava sources and flowing lava. From the guides they should not be able to spawn in any liquids.

To replicate: 

1. Find a basalt delta lava lake
2. Drink a fire resistance potion 
3. Stand at the bottom of the lava lake 
4. Watch magma cubes spawn 

Acceptance criteria:
To match java edition no magma cubes spawn in lava sources or flowing lava