I don’t think any major problems have been reported in Europe where there are already lots of offshore windfarms, sounds like scaremongering.
The report claims to differentiate between future US and existing European wind farms, so there might be something to this.
I downloaded & skimmed the report, and it is NOT an actual study, but a theoretical survey of the potential problems (since there aren’t any large US wind farms to be studied yet!). They make a number of assertions, some of which seem plausible to me, while others seem far-fetched. One assertion they make is that the majority of deployed marine radars are magnetron-based, rather than solid-state, which they feel is a potential negative due to the inability of these radars to discriminate against multipath and phase distortion In the yacht world I’m familiar with, this ratio is rapidly changing, but I don’t know what the situation is for big iron.