Hopper model only updates when an adjacent block is placed/broken or the hopper is interacted with

[Single player issue. May also affect servers, can't personally confirm]
1. Place a Lever on the top of a hopper
2. Toggle lever so it is powered
3. Hopper will not lock until the user interacts with the hopper
opposite state conditions have the same effect.

I am creating a texture pack that uses alternate textures when a hopper is enabled or disabled (green/red) and the texture does not update untill i either place/break a block adjacent to it, or open the hopper's gui (interact).

I would like the texture to update live as items flow through (for example) an item sorting system or a simple hopper timer.

a redstone torch changes state and switches textures/states immediately, why not any other block with alternate states?
(i'd assume hoppers may not be the only block with this issue. will modify this i if find other blocks with this issue)

-Redstone enthusiast. Thank you.