I believe thats quite an overestimate. Both Amazon and Google exceed the minimum required wage in each level on average by 93% and 73% respectively.
Separately, that is precisely what the article is doing. Conflating the minimum with wages actually paid to infer that H1B workers at large tech companies are underpaid.
Source: p52 on https://www.dol.gov/sites/dolgov/files/ETA/oflc/pdfs/DOL-Int...