Well, they are platform, not wall, that's why the bullets does not get affected by them. Also I prefer that it work like that, making them block bullet is kinda annoying honestly, cause you could just always go behind them and then easy, like the second phase would be hella easy if that was the case, that when they don't, the second phase is really hard.
Also the difficulty is what i'm mostly going for, I like game when you need to react fast and need to constently move.
And thanks you !