I mean, it isn’t the strongest quake in 25 years. Unclear why the source is making that claim. From what I can tell, the 2004 Indian Ocean earthquake and tsunami is. There have also been quite a few stronger quakes than this one in the past 25 years - I started making you a list and quit when I realized I’d exceeded 5.
My best guess is that the source meant strongest quake in 25 years in Taiwan, but why not actually say that if they meant it?