You're still tying to mislead. Even if you use your old numbers, 37 saves and 18 blown saves is closer to 30%. But a lot of his blown saves were really "blown holds," but no stat sites differentiate between the two. As Barnes spent most of 2018 pitching in situations where he was not going to get a save but was able to get a blown save, the overall statement is misleading.
Iglesias did do better than Barnes, blowing 14% of all save/hold opportunities. But Barnes actually rate was 24% of all save/hold chances blown. Less than the 32% if you only look at saves, and certainly less than the 50% which is just flat out wrong no matter how you look at it.
Of course, there are other aspects that are incorrect, too. 1) How many blown saves did the Sox still win? Blown saves are not all losses, after all. And how many were blown saves where Barnes did nothing wrong? Coming in with the tying run on third and no one out and giving up a sac fly is a blown save, but is it really the fault of the pitcher getting the blown save?