It will definitely help the market and shift away dominance from Bitcoin and spreas it across multiple coins.

Coinbase is the only large exchange that has less than 5 coins. Looking at the other top 5 exchanges, Binance., Okex, they all have dozens or hundreds of coins.

That means, any new coin only gets a slight bump in price, since it has to share that new buying volume with hundreds of other coins

However, wheen a new coin is added to Coinbase, it gets a lot, a lot of new buying volume.

That means that the new coin(s) probably maker gains of 100%+ percent.

So, it definitely help if Coinbase adds more coins than fewer coins, as it shifts dependency off of Bitcoin and makes their price less dependent on the Bitcoin price.