Thought boomer should deal damage to enemy after being killed with physical attack as it’s a dimensional type. When it’s killed, it just pull the enemy and not dealing damage.
Brony and The Glob do the same as Boomer, they are made like this on purpose because they no have base attack. If you look, all the dimensionals do their base damage when being eliminated and this increases according to the Phobies level; but the buffs do not affect this, do not expect that Grimes deal back 1.000 of damage when dying.
That is as intended! Even though Boomer is a dimensional, they do 0 damage. Therefore, they would do 0 damage upon death!