Welcome to Shipspotting Forum, Kern Jack
You are correct - this ship should not be in "High Speed Vessels" and I would like to express my apologies on behalf of the Admin team. Although we have a slightly different criterion this ferry is not fast enough to meet it: she is listed as "Max. Speed: 23.75kts, Service Speed: 22.00kts"
HIGH SPEED VESSELShttp://www.shipspotting.com/support/faq.php?category=Passenger%20Vessels
High Speed Vessels must be capable of 30 knots and be Passenger Vessels such as Jetfoils, Hydrofoils and Fast catamarans. In Equasis and similar, they may be shown as Passenger Vessels. This may well include vessels that could also be classified as Ferries, Harbour Tour Boats and Commuter Vessels.
I cannot tell for certain which of my colleagues has been mistakenly moving this image, but I will remind them all not to make such changes without checking data first.