Maybe but the estimate is quoted as "should be 48.9Mbps" and "generally within +/- 1 or 2Mbps".
Not even close, so totally misleading.
It still doesn't explain why my actual download rate plummets then remains at the lower level as though it was capped, it explains why my ip profile changes to match the lower rate prior to a reboot. It literally hits a wall at for example "27.83Mbps" and does not rise 0.01Mbps above the rate, literally every speed test hits exactly "27.83Mbps" as if there was just nothing more there to give.
BT (and I might add most other ISP's for that matter) get away with far too much as far as what we the paying customer are sold and what we are actually receiving.
Speaking as someone who is employed in a global industry the general population in the UK are far too accepting of poor service IMHO.