But the air certainly moves fast enough at the moment of taking off, and if the sensors are sensibly sensitive, they should register AoA well before V_1.
EDIT to add:
Hm, Boeing states:
"During rotation, pitch angle is the critical parameter that ensures tail clearance. Once the airplane is airborne and at a sufficient altitude where ground effect and crosswinds do not affect the sensor reading, AOA will provide valid information."
Looking at the FDR for Ethiopia [1], it looks like the AOA sensors disagreed 2 seconds before they left the runway.
The sensor disagreement happens after 05:38.43, they started climbing at 05:38:45 and were at 1000ft at 05:39:06 ish if I am reading the PDF image correctly.
EDIT to add:
Hm, Boeing states:
"During rotation, pitch angle is the critical parameter that ensures tail clearance. Once the airplane is airborne and at a sufficient altitude where ground effect and crosswinds do not affect the sensor reading, AOA will provide valid information."
https://www.boeing.com/commercial/aeromagazine/aero_12/attac...