The gamerules "waterSourceConversion" and "lavaSourceConversion" are absent in Bedrock Edition. They were introduced to Java Edition in version 1.19.3.

https://www.minecraft.net/article/minecraft-java-edition-1-19-3

Added waterSourceConversion and lavaSourceConversion game rules

• When set to true, allows new sources of that fluid to form
• Defaults to true for water and false for lava

Steps to reproduce:

1. Enter a world with cheats on
2. Go to chat
3. Type:

   /gamerule waterSourceConversion

   /gamerule lavaSourceConversion

Observed results:
There is no /gamerule waterSourceConversion and /gamerule lavaSourceConversion in Bedrock.

Expected results:
It should be there in Bedrock as Java has it in Java Edition 1.19.3.