Not quite; Luke has possession of the Kaiburr shard for maybe ten minutes before it's taken from him. He never has it again. The shard doesn't measurably affect his use of the Force. Primarily its plot purpose is to send him on a hunt for the main crystal, which is supposed to be so powerful that you become a Force God when using it.
I heard somewhere that a later novel tweaked the concept to say the Kaiburr isn't that powerful anywhere other than where they found it (spoilers), which is why they didn't win the war ten minutes after the end of the novel.
I guess at that point it becomes just one kaiburr / kyber crystal among many.
I did know about the intent for SotME, but never heard about those earlier draft concepts.
Thanks!
I heard somewhere that a later novel tweaked the concept to say the Kaiburr isn't that powerful anywhere other than where they found it (spoilers), which is why they didn't win the war ten minutes after the end of the novel.

I did know about the intent for SotME, but never heard about those earlier draft concepts.
Thanks!