When it comes to adventure bike tyres with aggressive treads, speed ratings are largely academic. There is a vast difference between running a tyre on the autobahn or against a drum in the factory, compared to our rough potholed roads, gravel and a variety of off road surfaces. These surfaces gradually weaken the tyre carcass. If you regularly ride your bike off the highway, limit your maximum speed when on it or on good secondary tarred roads. The bike manufacturers all have warnings in the manuals to restrict maximum speed to 160 when using knobbly type tyres and if you look at a TKC80 meant for heavy bikes, you will see it has a Q rating (160 kph)
Aggressive tread blocks also flex more, causing the tyre to work harden in the areas of flex, which leads to cracking. The likelihood of it happening increases with low pressures, high loads and continuous high speeds. Also bear in mind that if you ever had a puncture, regardless of whether you use a tubeless tyre or not, the tyre is damaged and all manufacturers’ warranties fall away, as well as speed and road ratings.
One last thing about speed ratings. The rating indicates sustained maximum speed. That does not mean running indefinitely at that speed. It means 10 minutes.