100% I think it's optics.
It reminds me of those police drug busts where they take a picture of all the drugs and it's just like a couple small bags, but they'll run the press release like "hundreds of lives saved!"
Acting like there are going to be millions of voters purged serves both party messages right now.
I'd say it serves multiple purposes. Optics is certainly one of them "look upon my works, ye Republican...".
But I think another perspective is a more dangerous effort to chip away at state responsibility for the process and procedures of voting. Once this is owned or easily influenced by a national institution then a single-party state disguised as a republic becomes far simpler to implement.
The danger here being that our system has relied on decentralized states handling these tasks and thus has not created the guardrails necessary (if ever they could survive a unitary executive theory) to ensure fairness.