“Natives” meaning they’re born there, but their parents or grandparents are usually immigrants. The “native born” statistic is a tremendous argument for stricter immigration controls, as the cultural influence towards terrorism is so high that it can affect even the native born population.
Ignoring NI-related terrorism, that is true (many of whom likely have ancestors who lived in Ireland before the English conquest). But it is perhaps however telling that it's effectively never the immigrants themselves, which leads to questions about why later generations end up involved in terrorist groups. The answer often appears to be cultural disenfranchisement due to not being "British" enough while also being tainted by family as emigrants.