The internet traffic is quite big for one full node already, if you put more than one, it'll be even greater, and that may attract some curious eyes too.
That's all that came into my mind. Plus, I would do IBD for only one node and then copy the data to all the rest.
Ignoring the initial downloading of the Blockchain. I can't imagine it bringing too many eyes when compared to what an average household would use for streaming services, and the like. Fortunately, we're in the age of streaming, and people are downloading their content constantly which has meant the traffic usage is much higher. I don't think three nodes would bring too much attention from a privacy stand point. I guess if you're streaming, and running the three nodes it would just add additional usage, but again certain households would use a lot more than the average anyhow.
I believe they were NeuroticFish was referring to the upload usage that would be coming from my network, this would indeed be different from other users on that ISP, but I don't believe it would be enough to cause much attention to be brought onto me.