It's hard to say Moreno is significantly outperforming Rutschman. It's true he's been better and the biggest thing in his favor, like you said, is that he's younger. But Rutschman's numbers look incredibly clean. He's building his 164 wRC+ on a .304 BABIP and a 17.6% walk-rate, which is slightly higher than his 17.0% K-rate and lends to a .426 OBP. Those at least look like sustainable numbers.
Moreno's 188 wRC+ is built on a .415 BABIP. Despite his average being 81 points higher than Rutschman, his OBP is only 4 points higher because he only walks 7.4% of the time to his 17.4% K-rate. Now, I'm hoping the low walks are only a result of him finding so much success with the bat right now and that he'll develop that ability to take the free base when he realizes you can't always spray the ball all over the field at a > .400 BA clip, but there's also no reason to assume that will happen because he's got 764 plate appearances in the minors at this point and has never shown a sustained ability to draw walks. In fact, his current 7.4% walk-rate in 2021 is the highest of his career so far and is likely in part due to pitchers pitching around him out of fear of the elite bat-to-ball skills he seems to have fully unlocked this season.
That being said, Moreno's age alone gives him a massive leash and the fact that he plays at a premium position with a seemingly positive reputation as a defender and as an athlete means there is a massive amount of room for failure here. He'll definitely skyrocket up prospect lists.