For what it's worth, both Heathrow Express and GWR's websites today showed the VbV window but ultimately approved the payments without additional prompts. (I was using the CSR, if that matters.)

As for US based sites, I think United showed something similar when I was paying the fees for my award ticket. That also went through with no issues or additional prompts.

Maybe Chase just went ahead and enabled the necessary support for all CSR cards so people wouldn't need to call in and ask?