The functional blocks item group contains blocks that have some kind of unique function, such as a user interface, recipe interaction, container, or display of text or patterns. One particular inclusion is blocks that emit light; this seems to establish that blocks with properties that deviate from the norm are included within functional blocks.

However, blocks with a property of slowing down the player when the player steps on them are not included in the functional blocks item group. The following blocks are not included:

• Soul sand
• Honey blocks
• Slime blocks
• Cobwebs
• Ice
• Packed ice
• Blue ice

Because movement speed modification is a unique function of these blocks, I would expect that they appear in the functional blocks item group within the creative inventory.