Different baffle designs work differently depending on what you're shooting through it. For example, the baffles on most 5.56 silencers are designed quite a bit differently than the baffles on most .22 silencers even though the bullet is very similar in size; the 5.56 silencer doesn't just have a larger size with stronger construction. Here's a cutaway of an AAC M4-2000:
Here are the baffles on a Spectre II:
And here are the baffles on an Element 2, which is a more typical .22 baffle design:
So it appears from your testing that the Spectre 2 was more efficient when firing lower-velocity, lower-pressure rounds like .22, and the Form 1 silencer had a baffle design that worked better with the higher-powered .17 HMR.