There's a bug when it comes to fires on Bedrock when you have fire tick/spread turned off.

Steps to reproduce:

1) Turn gamerule dofiretick to false.

2) Use a flint and steal to set the top of tall grass on fire (scaffolding is also easy to reproduce this with).

3) break the tall grass (or scaffolding).

4) walk through the block where the fire was.

If you stack the scaffolding up 3 high, and light the top one, you can walk under the block that's invisible fire easily, and then jump up and light yourself on fire.