Just a quick question

I'm currently reading through the first book in the vaults of terra series and I have a question regarding timeline. Does the vaults of terra series take place before guilimans return to terra? My theoretical to support this is that 1) I am halfway through the book and guiliman has not been mentioned by name once and 2) I am aware from my other reading that there was a coup attempt by highlords of terra and this book feels like it might be set up for that.