Data speed below sales pitch. 70% of line speed seems to be an acceptable "best effort"

I upgraded my FTTH line to a 100/100 connection in September 2020 and since then I consistently only measured 90-94 Mbps and never reached the advertised 100Mbps speed. VOX is rather adamant that their contract stipulates "best effort" and adds that the tolerance level for this should be about 70% of the line speed - in other words, they would be very happy that they have delivered "best effort" even if my 100Mbps line only delivered 70Mbps. Ticket numbers VOX***3 and VOX***0 has reference.