DoorDash's CEO says AI-led productivity isn't everything.Bloomberg/Getty ImagesTony Xu says AI boosted productivity at DoorDash, but it hasn't yet changed the workforce structure.DoorDash is focused on unifying its tech stack and making all employees AI-capable.Unlike other tech execs, Xu emphasized AI productivity gains without workforce reductions.One tech CEO says AI has not yet changed his workforce structure."We're seeing a lot of productiv…