How legit are Clearlake Capital's stellar returns?

According to Calpers their fund returned 40.8%, 32.2%, and 49.5% respectively for vintage years 2012, 2015, and 2018. That's some insane performance and I'm wondering if anyone here has any insight into the accuracy of these numbers. If they check out, what has made their performance so great? For reference, H&F's best fund (2011) stood at 24.7% and Blackstone's and Apollo's best were in the mid-30%, but this was from pre-2008. What's Clearlake's edge? How have they been so consistently high-performing?

I've seen other threads talk about their liberal use of single-asset continuation vehicles as the source of their high IRR. How, then, do continuation funds help inflate IRR and why don't more funds take similar steps to artificially boost performance?