It is easier to assume a local source or at least stellar distances to get rid of a number of unnecessary assumptions. At the same time the signal embeds the factor five and eleven. That makes it a pretty clear beacon that allows location confirmation. Could these be navigation tools used by space ships to confirm their location?
We are seeing these rarely because we are not always looking in the right area of the sky or looking for just this.
Such a beacon or beacons would allow superior location resolution in local space where it is likely to matter. .