Yes, after they were in-galaxy. The signatures from cross-universe 'ports would already be gone, left behind in the Seeder space, which would be suicide to go into.

And again, there are bombers in this day that show up as a sparrow on radar. Imagine the bombers of a race a thousand times more advanced. We wouldn't get a single thing from them at that technological level. Disturbance? Yes. Enough of a disturbance to say "Direct intervention needed"? Probably not, unless one is fool enough to waste time and fuel to check in on a ripple.