The law has you pay taxes of 1% of gross revenue * percentage of global employees working in an SF office. Even if the headquarters moved (and I'd guess it is already a Delaware registered company legally), they'd still have to pay.
For example, if you have $10M/yr in tax incidence and 100 employees all in SF, you could have an on-paper workforce of 1000 Nigerians at the national median wage of roughly $1k/yr, saving $9M/yr in taxes.