Yeah, she's an idiot, and that's a load of crap for those with no curiosity in finding out the truth. It seems like they're trying to employ the tried and true tactic of "baffle them with bullshit" when the truth is problematic for them.
There are any number of tactics that could have been used to secure the roof of that building, including blocking the line of site. I will speculate that the Secret Service did not have the manpower to do their usual thorough job. That means the investigation needs to be going up, org chart-wise. They better keep digging, because the utter lack of transparency about this assassination attempt is quite worrisome. Trump might do better to hire his own security.
Mayorkas (or however that klown's name is spelled) said that Trump had a full Secret Service detail, but according to Dan Bongino, the agents on Trump's team asked for more. Somebody is lying, and given how often Mayorkas lies about everything else, chances are very high that it's him.