This ticket concerns an unannounced model change from 1.8; as said change is unannounced I've reported it as it may not be intended. I personally prefer the result of this change and would like to see this ticket resolved as Works as Intended, however such a decision is ultimately up to Mojang. More information below.

The bug

When levers were converted over from hardcoded rendering to block models in 14w10a, this resulted in changes to their appearance. For example, smooth lighting affected their main body considerably less (likely due to improved UV handling), however the "handle" part of the lever also gained directional shading.

Since Bedrock Edition has yet to convert blocks over to models, this technically also constitutes a parity issue (although the change in question happened considerably earlier than the 1.15/1.14 deadline).

How to reproduce

1. Place levers
2. Pay close attention to the handle, and note how it appears darker or lighter on different sides
3. Repeat this test in 14w08a or earlier
4. Note how the handle appears equally lit from all sides in these versions

Expected results

The equally lit handle would remain so in current versions.

Actual results

It appears shaded differently on each side in modern versions.

How to fix

If this is determined to be a bug, it can be fixed by simply adding a "shade: false" line to the handle element in the lever models.