I'm starting to think the entry about his artificial arm should be removed.
Fact 1: In Guitar Superhero, he states that without his exosuit, he's just a regular guy.
If his arm was artificial, he would have used it as a weapon, assuming it is stronger then a normal organic arm.
Fact 2: In Lab Rats vs. Mighty Med, Horace is completely unfamiliar with bionic technology, which would include artificial limbs.
As that was just a teaser video, it most likely was just made up for Rule of Funny and contradictory facts should not be taken as canon.