well, Gus is super careful when he starts business with Walt/Jesse, this on other hand, was extremely reckless. Not only was he risking Nacho's life, but also a war he tries to avoid in the first place. So yeah, I accept it as a cool scene. Also, I know Nacho has some of Lalo's trust, but Lalo's intuition probably would make him put some eyes on Nacho. There was little reason for Nacho risk/reward-wise to go spiderman to retrieve those rocks aside from gaining Lalo's trust, and an alarm should've went off.
This is still 4 years before the first season of "BB". Gus ain't quite yet the Gus we know in "BB". When talking to Schuler in the hotel room he admits they'd lose a war with the cartel. Obviously that's not the case by the time "BB" rolls around. So I chalk it up to him having to be a bit more "hands on" at this point.
Nacho, even before Lalo trusted him, was still 2nd in command after Hector got fukked up. I don't think Lalo would suspect anything, he probably thought Nacho was taking initiative to save their investment. Lalo is perceptive but I don't think anybody would read that situation as "he's trying to earn my trust". Worse case scenario they'd think Nacho is crazy.
Fred.