Not entirely true.

It is still relevant as to how the state legislature is broken down, but yes, it is less relevant. For example, let's say for simplicity's sake that Texas had 4 million Dems & 6 million Republicans, leading to a 40/60 split that we would hope to see reflected in the govt body. If there were 10 legislative seats, each representing 1 million people, we could carve up 10 districts — 1 district that had 900k Dems and 100k Republicans, and the other 9 would all have 344,444 Dems and 655,555 Republicans, leading to an easy 90/10 split for Republicans.