People always say this sort of thing when talking about distant events, it's not actually true.
When we're talking about long distances then the relativity of simultaneity comes into play strongly. There is no universal ordering of events, there is a substantial degree of relativity to ordering of events that are separated by great distances. And, in fact, the only hard boundaries on this ordering are the "light cones" connecting events. In one reference frame the M82 supernova could have happened 12 million years ago, in another reference frame it could have happened a year ago, or two years ago, or even 20 million years ago. In the reference frame of any neutrinos that happened to have been created in the supernova it would have occurred mere seconds or hours before the first light reached Earth.
When we're talking about long distances then the relativity of simultaneity comes into play strongly. There is no universal ordering of events, there is a substantial degree of relativity to ordering of events that are separated by great distances. And, in fact, the only hard boundaries on this ordering are the "light cones" connecting events. In one reference frame the M82 supernova could have happened 12 million years ago, in another reference frame it could have happened a year ago, or two years ago, or even 20 million years ago. In the reference frame of any neutrinos that happened to have been created in the supernova it would have occurred mere seconds or hours before the first light reached Earth.