Summary:

On the campfire, you can place a "block of fire" from the side with a flint and steel or fire charge.

Steps to Reproduce:

1. Place campfire
2. Remove the next lower block 
3. Setting fire to the side of the campfire

Observed Results:

Campfire will light up from the side.

Expected Results:

Campfire will not ignite.

Video:

Minecraft 2021-02-13 13-24-02.mp4