This is a regression of MCPE-187403 which was fixed in 1.21.50.25. The bug reappeared in 1.21.50.28.

Pale Oak Leaves are lighter on Bedrock Edition than Java Edition due to a different ambient_occlusion_exponent value in blocks.json. Having a brighter canopy detracts from the spookiness of the Pale Garden.

Comparison GIF:

The Pale Oak Leaf brightness is most obvious when you replace the textures of Pale Oak Leaves and a normal block like Dirt with a plain, white texture (see the attached pale_oak_leaf_brightness_gamma sample pack).

There is more shading applied to the Dirt than the Pale Oak Leaves, despite using identical textures.

North-South

East-West

Bottom

Expected Result

Pale Oak Leaves are equally bright on Bedrock and Java Edition.

Observed Result

Pale Oak Leaves are brighter on Bedrock than Java, detracting from the gloomy atmosphere of the Pale Garden.

To Fix

Set "ambient_occlusion_exponent" to 1.0 in the 1.21.50 blocks.json file.