I was referring to bank cards earning 3x points that you can then transfer to the carrier of your choice or use for other travel or cash back. Amtrak competes against all cards in that regard and not just those that are carrier-specific.
I still think it makes more sense to compare them to what's offered for cobranded cards, versus large bank cards with transferable currencies. The cobranded cards are meant to build loyalty, not just maximize points earnings, and offer many carrier-specific benefits that the bank cards with transferable currencies don't. Particularly in the ~$99 range, the options are basically cards that will offer a bit better earning rates plus the option to transfer, or the carrier-specific card with a bit weaker earning but helpful perks when traveling. There's also the TQP boost for those who value that.
I think Amtrak's better strategy would be to see about partnering up with a bank or two to be added to their transfer partner base, rather than try and fit too much into a cobranded card. I wouldn't be surprised if the transition to FNBO might enable that - I could see Amtrak wanting to get rid of a "non-compete" clause so that they can cash in on transfers from multiple large card issuers. There's almost certainly money to be made there, and might get people interested in taking Amtrak that otherwise wouldn't have considered it.