The laws here are from the 20th century, no obligation for transparency what so ever.
I've asked but "no one knows". Then I confronted them with independant measurements of speedtests, compared their results to different local isp's, and compared their own ookla speedtest servers to impartial speedtest servers (with significant differences in performance of course), but still no clear answers on how that is possible, only denial.
So, I' m back to my original question. Are there any tools that can detect and proof bandwidth throttling?