yea it's desired thing, not a bug. also, the unit is my favorite one because of this.
btw you may find interesting the combination with Inone Two Oldest(!), who summons an imp on sacrifice, and lvl-3 executioner will spawn 3 such imps and... anime. :D the only problem is to find an optimal way to make Inone be as strong as possible.
endless mode is cool idea! i'll think it over.