It does apply to later rounds, but the situation in the seed round is much different. In a seed round, you have the option of raising from either angels or VCs, including potentially many different VC's. This gives you some control of the situation and changes the signaling risks as compared to raising a series B.
Even more importantly, as Elad mentioned a VC firm can do many, many seed investments per year without much cost to them, but is very limited in the number of Series A investments. The rate-limiting resource here is time more than money; a VC can only sit on so many boards. While this makes a Series A investor passing a worse signal than a seed investor passing, the former is in practice much less likely to happen because of how resource constraints work.
Even more importantly, as Elad mentioned a VC firm can do many, many seed investments per year without much cost to them, but is very limited in the number of Series A investments. The rate-limiting resource here is time more than money; a VC can only sit on so many boards. While this makes a Series A investor passing a worse signal than a seed investor passing, the former is in practice much less likely to happen because of how resource constraints work.