There is currently no known projectile that can take out a single room in a suburban concrete building with such precision without collateral damage, even less one that cannot be detected by radar and can be delivered by a stealth aircraft. Of course there might be technology we are unaware of, but it is highly unlikely just due to the physics behind it. (And which obviously did not lead any parts behind)
But it is a huge embarrassment, even a major risk for their lives, for the Iranian security services and some of their higher ups if the story about the planted bomb is true. Because that means even very elite Republican guard units and officers are either very very bad at their job - or a Mossad asset. Both are a major risk for the political elite in Iran as both the embarrassment towards the public and especially their own allies, but also possible infighting/blamegames are a danger to the current status.
So I wonder which theory is more likely to be true: A mysterious wonder of a projectile or a political regime lying.