It is a small leap. The balance in your bank account is also a number without a physical presence. It has value because you can convert it to physical goods. The same is true of a Bitcoin balance.
Currency is a contract, it's inherently intangible.
Bitcoin is not a currency, and it's not used for anything, so it's a really just a number, that someone may speculatively want to pay money for, due to the fact a small number of other people will pay for it, but unless there's a more broad acceptance of it, the implied value will also fade.
If NFT's implied ownership of the Baseball card itself, I think this would be another thing altogether.
Yes, the value of the Baseball Card is derived from the fact that it actually exists.
The fact that someone is arguing that 'The Baseball Card' is not materially different from 'a number' is really an interesting cultural phenom.