It stretches credulity that they could get anything near 4.5 billion unique visitors when their most popular site only gets 0.4 billion [0]. But even if that were the case, 4.5 billion is still less than Google and Facebook combined. (Of course it's not valid to stack Google and Facebook's visitors as disjointly unique, but the same is true of Pornhub and its properties.)

Regardless, you're totally right that their numbers are relatively impressive and indeed "Google-scale" if we interpret that as within an order of magnitude. If the metric they used was "unique visitors per employee," then even with official source numbers they would be around 10x as successful as Google!!

[0] https://www.statista.com/statistics/1201889/most-visited-web...