The new wood-like blocks are meant to not burn, and the Warped and Crimson stems, stripped stems, fence posts and fence gates all cannot be used as fuel in a furnace like their wood counterparts can. However, the Crimson and Warped stairs, slabs and planks can be used as fuel in furnaces. These should not be able to be used as fuel as they are meant to not burn.
Linked issues
is duplicated by 5
MC-171088
Inconsistency: Some crimson and warped items usable as fuel; others unusable
Resolved
MC-171209
New "Fireproof" planks and items can be used as fuel!
Resolved
MC-171284
Crimson/Warped planks are usable in the furnace
Resolved
MC-171524
Crimson/Warped wood blocks can be burnt as furnace fuel
Resolved
MC-173502
duplicate
Resolved
relates to 2
Comments 2
Still occurs in 20w08a.
Possibly related to https://bugs.mojang.com/browse/MC-171830 and https://bugs.mojang.com/browse/MC-172279
Can be used as fuel: signs, stairs, doors, planks, slabs, buttons, trapped doors, and pressure plates
Cannot be used as fuel: fence, fence gate, stem, and stripped stem.