I don't like the idea of national governments owning Bitcoin, and while US gov spending money on acquisition of BTC is far less bad than most of what it spends money on, I still prefer private money to be held privately.
However, if a digital asset reserve is going to happen, I strongly believe it should be Bitcoin only. I say this as someone who obviously supports many crypto assets and projects.
Bitcoin is, objectively, the most liquid, the most safe, the most trusted, the most decentralized, and the most conservative digital asset on Earth.
There is zero defensible reason to include any other digital asset in such a reserve, at least today. With time (years?), it would be reasonable to consider adding other things, but those are discussions to be had years from now.
Start with the strongest, most defensible foundation. Understand it. See what effect it has with some time. Do not complicate the novel idea by adding the complexity and risk and noise of other digital assets.
Bitcoin only, in this case, and at this time.