Yes, if “GC can quickly expand to contain the volume over which its panspermia of origin occurred”, when we return to the model of intergalactic grabby aliens. But if the panspermia volume is relatively large and the speed of colonisation is relatively small, for each such volume there will be several civilizations which appear almost simultaneously. They will have age difference around 1 million years, the distance will be less than 100 kyl and they will arrive soon.
We will encounter such panspermia-brothers long before we meet grabby aliens from other remote galaxies.
Yes, if “GC can quickly expand to contain the volume over which its panspermia of origin occurred”, when we return to the model of intergalactic grabby aliens. But if the panspermia volume is relatively large and the speed of colonisation is relatively small, for each such volume there will be several civilizations which appear almost simultaneously. They will have age difference around 1 million years, the distance will be less than 100 kyl and they will arrive soon.
We will encounter such panspermia-brothers long before we meet grabby aliens from other remote galaxies.