They They could hire a smaller of more qualified and invest more into automation.
The only reason Google is doing this is because they don't want to spend the same amount on benefits and other overhead on 15$ per hour worker as they do for a 30$ per hour one.
They have the $15/hour contractors lugging batteries, hell yea they should invest in automation, but unfortunately as you point out the legal environment does not incentivize them to do so.
$15 is already equal to the proposed federal minimum wage under the current administration. They should automate because lugging batteries isn’t a healthy fit for many of the humans that they are attracting at this low wage.
However working in an Amazon warehouse or a McDonald's is? It's not unlikely that a significant number of people lugging batteries at google would be forced to do that since Google would have no reason to hire them the.
The only reason Google is doing this is because they don't want to spend the same amount on benefits and other overhead on 15$ per hour worker as they do for a 30$ per hour one.