The bug
In the Creative inventory, mangrove planks products such as the block itself, planks and fences come directly before the nether wood versions. However, stairs do not seem to follow this, instead being placed considerably after them.
How to reproduce
Open the Creative inventory to Building Blocks
Locate mangrove stairs
Locate the two nether wood stairs
Expected results
Mangrove stairs would come directly before crimson and warped stairs.
Actual results
They appear several lines later.
The main problem here is that all the wood stairs are all over the place.