We have 1 possibly-armed-with-a-handgun guy of unknown intent and ability on a porch, vs 5+ SWAT officers who are definitely trained in shooting people, are in cover, have body armor, rifles (presumably good ones with scopes and whatever else), and high-powered lights trained on the house.
So yeah, I would say they should wait until a suspect starts shooting because they have an overwhelming tactical advantage. Yes, that's a risk because the guy on the porch might be John Wick or Jason Bourne or the Terminator, but most people, even most professional criminals, are not expert marksmen under any circumstances, let alone ones where they're at a large tactical disadvantage.
Next time you meet a cop socially, ask them if criminals are smart or supervillains 'like in the movies' The cop will laugh and regale you with stories of how dumb and inept most criminals are. Police know perfectly well that most people don't have a clue, are easily intimidated by police, and not super-skilled. Sure, they have to consider the small number of dangerous exceptions, but overstating the risk factors is also a really convenient way to get off the hook for their own poor firing discipline.
What do you think will happen if a shirtless man on a porch a pulls a pistol, while you have your high powered rifle's scope locked on their chest while you are wearing body armor, positioned behind a police car, a few hundred feet away?
This was apparently a SWAT team that initiated a confrontation in response to a report of a situation involving firearms. Why weren't they already behind cover so that if the guy really did come out of the door shooting at them, they were protected? And if they were, why was it necessary to shoot first when the situation obviously wasn't clear at all? Nothing about this adds up.
