What happens when ALSO's pedal-by-wire e-bike runs flat

The ALSO TM-B, an e-bike from the Rivian spin-off, has no mechanical link between pedals and rear wheel; pedalling generates electricity that drives the motor. One owner deliberately drained his battery to test it and found the bike steadily cuts maximum assist, dropping from boost Level 8 at 23% charge to Level 2 at 5%, before reaching what it calls 'Infinite Turtle Mode'.