Instead you just scan your boarding pass / smart phone yourself.
I can't imagine that this is in any way slower than a face scan.
Certainly when a borading pass, matched to a passenger who checked in luggage, is not used for boarding the luggage will be unloaded.
Identity check really depends on the airport and airline. Sometimes your identity is checked when you enter the secure area, sometimes at the gate and sometimes not all.
Even at airports that don't check identities airlines - notably budget airlines - may check id at the gate.
It may also happen that id is (spot) checked upon exiting the plane, but this is very rare.
That's only applicable for flights within the Schengen area. Passport checks upon leaving or entering the Schengen area are pretty strict. Essentially every piece of id is checked towards the SIS[1]. But within Schengen and depending on the airport there may be no checks at all.
[1] https://en.wikipedia.org/wiki/Schengen_Information_System
In Zurich your id is virtually never checked on Schengen flights. Last time I flew through Vienna security wanted to see the boarding pass, but not the ID. Dusseldorf also didn't check when I flew through it last (alas, a few years ago).