There are supplements that are only EPA but they are expensive. I vaguely recall the study you mention. Seems like it said DHA counteracts the heart health benefits from EPA if there is more DHA than EPA. I need to look at the study again to see if i have that correct.
You are correct. The study did talk about counteractive functions in EPA and DHA for heart health. There are other reasons for taking fish oil supplements such as brain health, so it’s a quid pro quo. I suspect there are concomitant factors in heart health and that DHA alone isn’t going to lead to a decline in cardiovascular health.