Are folding locks as secure as U-locks?

Generally no. Reviewers and r/ebikes threads describe folding locks as more convenient but easier to defeat than a heavy U-lock or chain. The FoldyLock Compact carries a Sold Secure Silver rating (versus Gold for the top Kryptonite picks), which positions it as solid mid-security rather than maximum security. Even fans on r/bikecommuting concede it won't stop an angle grinder.