I don't think so. They're comparing it to the highest tier available models from Anthropic and OpenAI. Generally speaking, Opus is better than Sonnet in almost every way, so why have the redundancy?
I think their comparison to how their benchmarks compare to Opus are a great way to show "look at similar benchmarks for a fraction of the cost". If it has Opus benchmarks (I don't actually take benchmarks seriously, but for their comparison purposes) and Sonnet is still more than half the price of Opus, I figure it's close enough where it doesn't matter.