Essentially, the lack of a bucket of experience makes it difficult to store the experience used by this mod in other mods, like Refined Storage. Since Refined Storage requires using a bucket to remove fluids directly from storage or to add filters on exporters, not having a bucket effectively prevents the experience fluid used by this mod from working with those other mods.

Additionally, it's not really feasible to ensure your storage always contains the experience from a different mod, because while it will be compatible, emptying the storage of experience and then adding some back will always use the SophisticatedCore version of the fluid.

Are you not able to use something like jei to drag the experience fluid over to refined storage filter?

Unfortunately not for fluids, with refined storage at least. It's kind of clunky.

Added this in 1.21 so it's available from there on. I don't feel this is critical enough to add in any of the previous versions.