Leaving aside excessive and largely ineffective security screening for flights in the US (and pretty much everywhere else), a lot of European high speed trains absolutely have metal detectors, luggage inspection, and document inspection. As do many buildings.

It doesn't take long to go through most of the time but then going through Pre-Check probably averages me 10 minutes. But I do leave a good buffer.

It's probably a bad idea to predicate travel time estimates on arriving at the train 3 minutes before it leaves and getting on.