There's no generic way to know the hashrate unless the pool mines something. Those metrics infer the hashrate from the number of blocks mined in the last 24 hours.

You can't know the works other are doing unless that work earns them a block. And then it's just an estimation of their hashrate because luck is involved.

In their pool website you can see the hashrate, but just because the share difficulty is much lower than the block difficulty.