I always need to see a manned immigration desk due to the type of my visa. I always ask for an immigration form during the pre-arrival service ( if they haven't distributed yet ) and they simply hand an immigration form to me after the service is completed.

I also had an experience at JFK ( not BA Terminal 7 ) where the immigration officer asked the same "yes no" and "do you have anything to declare" questions as a conversation instead of an immigration form which wasn't distributed by the airline that I've flown.

In addition to this in all BA flights to IAD that I've flown in the last 6 months ( 2-3 times ), the crew had announced that passengers could use the kiosks if they have a valid ESTA or holds a visa that has been used before to enter the USA; however in IAD, there is no kiosks except for the Global Entry and Mobile Passport lane. All residents and visitors without Global Entry and Mobile Passport are asked to process at an immigration officer at IAD where an immigration form is required.