Mob Spawners drop a static amount of experience, irrespective of any enchantments that have the `block_experience` component. I suspect this was done to still drop experience when silk touch was present, but it means that enchantments which should increase the dropped experience are unable to do so for mob spawners.
This is because Mob Spawners use popExperience instead of trySpawnExperience in their spawnAfterBreak override.
Attached is a datapack which provides a pickaxe enchantment that multiplies dropped experience by 100, which makes the issue very obvious.
This issue is unrelated to MC-273411 which concerns `block_experience` not applying when present on a non-tool item.
Can confirm. I should note, though, that the attached file is not a data pack, it's a zip file with a data pack folder in it. Next time, try not to put the folder with the data pack files in a zip file, and instead put the data pack files directly in the zip file.