FWIW, USA citizen, Global Entry, MPC app on phone arrived American Airlines JFK T8 from LHR couple of nights ago, weeknight, about 8:00pm. Did MPC inputs while taxiing to gate, no bar code provided, app stated “go to lane 31”.

Get to Passport Control lines, many more people in the general line than I’ve seen since COVID (12-14 arrivals). No line for GE where there were only 3 kiosks (many fewer than I recall). Sign directing MPC users to ~ lane 33-34, get to front of ropes where there is 1 other person and a yellow striped rope closing the line with no apparent route to any lane and no staff nearby.

Wait 5-10 minutes, watched staff member yelling several times from ~lane 26 to the people lining up after GE at ~lane 34 to go to lane ~32, thus walking right in front of the 2 of us. Ask other person how long been waiting, said 5 minutes. Waved at yelling staff member without reply, finally walked to yelling staff member who said “go to lane 20”.

Went to lane 20, where a family of 5 people were waiting. Officer in that cubicle exited the cubicle and walked away on the far side of the cubicles with the 1 person who was in the cubicle. Officer returned 5-10 minutes later, called the family of 5 to the cubicle, spent 5-10 minutes chatting, then sent them through and called me to cubicle.

I handed the officer my passport and retired Navy ID card (which I do infrequently, only when I think I might “mouth off” too much), said “I did Mobile Passport Control, I’m retired Navy” (thinking it might expedite things). Officer was prior Navy, we chatted about our respective ranks and officer had several family members in the Navy including doctors, we chatted about medical specialties. Officer took my photo and waved me through, no further mention of MPC or GE.

I had asked the yelling staff member where Supervisory Officer (SO) was, knocked on that door. Told SO of my experience, SO said:
“sorry, it’s change of shift” and
“we’re short staffed due to 75 officers from this location being at the Southern Border”.

Edit: When I asked if MPC was still preferred by CBP, SO said “yes, please do MPC next time”.

Both the officer who screened me and the SO were gracious and polite and respectful, as was I at all times. But, overall process, even without the few minutes chatting with my screening officer and speaking with SO, took MUCH LONGER than all previous arrivals at JFK T8 during the past few years.