Pressure Cooker bomb, it means either Pakistani, Bangladeshi, or Afghani are involved. They had good practice on Indians.
Pressure cooker bombs have been around for some time as you say. The technology is widely available on the internet.
This style of bombing attack, the loose Saudi connection, non-government target, big crowd target, smacks of AQ.
I have read of pressure cookers in that general area. That’s what I thought of when I heard it - the India subcontinent area.