When a lightning bolt is created, it will attempt to detect a lightning rod 1 block below itself.
It does this correctly in ServerLevel.java tickChunk(), although right after that it runs lightningBolt.moveTo(Vec3.atBottomCenterOf(lvt8)); which offsets the lightning bolt before creating it.
That same check is done within the lightning bolt in powerLightningRod() where it checks the block below, but now that the block is offset it checks the incorrect block.

If you have a second lightning rod below, it will power that lightning rod instead

Reproduce

• Place two lightning rods one above and one below (see image for placement)
• do /summon lightning_bolt on the top lightning rod
  Notice the bottom lightning rod is powered not the top