I was also a bit hesitant when they mentioned coinbase, because even if they were referring to the Coinbase wallet App, it's not the best wallet reference. I'd be more comfortable if they mentioned alternatives beyond coinbase, wallets such as Electrum, Sparrow, Wasabi, BlueWallet, Green Address etc.
The mention of the partnership with Tether indicates that stablecoins such as Tether will be integrated, that is, we will not have a bitcoin-only wallet. This means that to support Tether there must be at least one network that supports this token such as ETH, TRX, etc. Adding more code and increasing complexity and the focus becomes not only on Bitcoin.
When choosing wallets, the majority prefer big brands than open-source well-reviewed self-custodial wallets that we usually use.
You can easily see how huge its userbase if you check the "Downloads" number stats of Coinbase Wallet app.
You're right, but for a new wallet in the space (or any new project), the first good impression is the one that always remains, so that later they don't have to rush to win users more hard in the future. Of all available options, will they use (or declare themselves competitors to) Coinbase as a reference?
To me (I might be wrong) this is a sign that they discovered Bitcoin yesterday and this could impact the user experience (or even the security) of the final bitcoin wallet app.
Still, it's always good to have more wallet options available, I could be a little wrong now, let's see what happens.