The Pale Oak Java feature definition contains the following weights:

{ "chance": 0.2, "feature": "minecraft:pale_oak_creaking_checked" },
{ "chance": 0.8, "feature": "minecraft:pale_oak_checked" }

Which comes out to a 20% chance of a Pale Heart Oak of being selected.

However, on Bedrock Edition, the Pale Oak feature is defined as follows:

[ "minecraft:pale_oak_tree_with_decoration_feature", 9 ],
[ "minecraft:pale_oak_tree_with_creaking_heart_feature", 1 ]

Which comes out to a 10% chance of a Pale Heart Oak being selected for generation.

The Bedrock feature weights should be changed to 8 and 2 to bring it into parity.

Additional notes following further research:

NOTE: It appears there is an apparent reduction in the number of Hearts in 24w44a, however, Bedrock is still generating far fewer than that new lower amount. Working on some experiments to match it.

It appears the weight isn't the main issue with the lack of generation. Changing it to 20% didn't make much difference. The primary cause of the lack of hearts is the single-column feature search in the creaking_heart_search_feature.json file.

What I did to solve the problem is create an add-on which changes the Y search of 0 to 6 to 3 to 6 (half the height) since those lower Y values are wasted CPU cycles since the Pale Oak is very unlikely to contain branches capable of hiding the Heart at its base. Then I used those extra cycles to increase the X and Z search to do a 2x2 search instead of a 1x1 search. Finally, to help the Heart appear in tiny Pale Garden biomes I raised the feature weight from 10% (see top of description above) to 18%. This gives excellent results closely matching Java Edition. Here's the segment of creaking_heart_search_feature.json which shows the search changes:

"search_volume": {
  "min": [ 0, 3, 0 ],
  "max": [ 1, 6, 1 ]
}, 

If 2x2 is too expensive to run on mobile devices perhaps remove the Heart placement check feature and instead modify the minecraft:tree_feature to include the ability to place a single block during its branch generation?

Steps to Reproduce:

• Create a new world in Creative Mode and locate a Pale Garden biome.
• Move around using /fill ~-20 ~ ~-20 ~20 ~8 ~20 air replace pale_oak_log and /fill ~-20 ~ ~-20 ~20 ~8 ~20 air replace pale_oak_leaves to clear the garden.

Expected Results:

The number of Pale Hearts should roughly match that of Java Edition.

Observed Results:

On Bedrock there are far fewer Pale Hearts available to the player, and in certain circumstances, none, even in medium sized Pale Garden biomes.