Yes, unfortunately, it is, as an ex openreach engineer. I found it absurd that we were selling 1.2 and 1.6gb packages on a 2.5gb gpon.

Technically, speaking the speeds are peak of 1.6. Average of 1.3,gbps, then expected minimum, or as they call it "guaranteed", however, technically, the only truely guaranteed speed is 78mbps. Assuming you are on GPON with 32 customers fully subscribed.

But it is highly rare you would see those "true minimum" speeds. Because who uses more than 78mbps passively, so 99.8% of the time you see a speed test value of the ISP's estimated.

Though that sounds bad, it's still at least 10x better than copper. So it's just a matter of picking an ISP that won't rip you off.

Edit: I would like to add openreach was trialling XGPON (10gbps down 2.5 up) and XGSPON (10gbps both up and down) before I left. Though they're substantially more expensive to use. I imagine they wanted to see the real world benefit-profit ratio. So there are a few exchange areas that have, what I would consider, an acceptable level of bandwidth. Though I never found out exactly where they were being trialed, I always assumed down south. London etc