This has been a disaster for months - it is not joined up, massive queues across airports in Europe. A number of countries have suspended it for the summer because it simply doesn't work properly and is unlikely to ever work. They had already delayed it's implementation by about a year.
Yeah, that's all fair. It would have been better if they had somehow had terminals at (say) local council offices in the UK where you could register at any time, rather than all in one massive go at airports (on arrival) or at ports on departure. I get the feeling that after two or three delays at turning the system on, because they knew it was going to be a problem, they eventually said "Oh putain!" and decided to switch it on anyway rather than admit defeat and have another 12-month delay. Even the aumtumn would have been better, which was an initial proposal... but in 2025, I think.
Having watched Europeans do their fingerprints at Geneva on normal passport control, some having to have several goes to get their fingerprints to register, and just the facial ones at CdG rejecting about one in five who have to go through the manual booths, I'm not entirely surprised.