Agreed - the transition is really seed to series A.
By the time you hit series B or C, you have investors who own a large part of your company already (and in most cases won't do an "inside round" - or if they want to do it, the entrepreneur does not).
So the dynamic post-series A becomes the VC helping you more in raising a B, but not competing for the series B. Since they are not competing to lead your B (they just pro rata), there is no signal (unless they do not want to pro rata, which is a very large negative signal).
By the time you hit series B or C, you have investors who own a large part of your company already (and in most cases won't do an "inside round" - or if they want to do it, the entrepreneur does not).
So the dynamic post-series A becomes the VC helping you more in raising a B, but not competing for the series B. Since they are not competing to lead your B (they just pro rata), there is no signal (unless they do not want to pro rata, which is a very large negative signal).