Just started a new game, and I'm about 2 hours into it. I decided to take up three dog's offer and install a new satellite on the monument. On the way, while listening to GNR, Three Dog announces something along the lines of " it has been three days since our friends in power armor kicked the Enclave butt" referring to the battle over project purity. Is this a known bug? Or is there some reason why he is announcing events before they even occur.

And to clarify, this has happened once before and I did reinstall the files on steam, but clearly that has not worked.

It's a Broken Steel DLC bug.
Look around the modding forums and you will find various attempts to fix this bug.

Thank you!