In previous versions of minecraft, flint and steel was able to create fire blocks on the sides of blocks regardless if it had a block underneath the area for the placement of the fire block or not (which would lead to disappear instantly). This might not seem much, but allowed builds such as slimeblock flying machines to work as piston would detection these temporarily floating fireblocks and trigger the BUD's that allow these slimeblock machines to work. However in 1.13, this is no longer possible if the block underneath the fire block is transparent or air. There are no changes for the fire block in the 1.13 update log, so I'm wondering if this change the mechanic of the flint and steel is unintentional, and I hope for it to be reverted.