In theory yes.
However, the tools which are offered by the official institution (Bundesnetzagentur), which should hold watch over ISPs and their service, do not even measure package loss. All they measure is throughput and ping. That alone is not sufficient for proper gaming. Also an average ping does not suffice, if there are short ping spikes, which average out over the measuring period. Basically I know more than the tool checks and the things the tool checks are often not the problem. Furthermore I have to go through a process of measuring so and so many times on a schedule. Add to that, that the ping spikes are sporadic, so that I would have to be lucky, to actually record any.
It is quite telling, that the official tool for measuring a connection offers so little statistics, that it is basically useless for people, who just need a _stable_ connection (no package loss, low ping, no ping spikes, OK-ish throughput). The official tool does not allow me to "prove it".
Basically, I could live with half my speed, if the connection was super solid. Throughput is not everything, unless you watch 4k videos all day, where there is lots of buffering happening anyway. Instead, they promise everyone (mostly people, who don't know much about IT) "high speed", at the cost of reliability.