The UK lives in the dark ages regarding Internet. In Switzerland I already had 150mbit internet (in 2010+) while when I moved to London I couldn't even get more than 16mbit while living in Zone 1. Still these days I can't get that speed.
DSL (running on the shitty, rusty phone lines) is allowed to be sold as fiber because fiber is involved at some point in the transmission (up to the DSLAM). By that standard, even 56k dial-up could be called fiber because there would be fiber somewhere in the datacenter on the other end.
HFC (Virgin Media cable) is also called fiber even though it's fiber to a certain point and then you're sharing a coax loop with dozens or even hundreds of people. It's even worse because the shared bandwidth can be saturated and the connection becomes unusable because of packet loss (could technically happen with DSL if the exchange's uplink saturates, but I've never seen it happen compared to cable networks).
There's also a naming convention of "superfast", "ultrafast", etc which creates more confusion. If you want to express speeds, how about you just quote the raw numbers?
Maybe this all will change when there is more Working From Home to be happening the coming years.
https://www.choose.co.uk/guide/exchange-only-line-fibre-broa...