Just observe your treehouse tree during the next storm: A 40 cm thick tree at a height of 2 m hardly sways at all, in a hurricane maybe 2 cm in both directions. At a height of 5 m it can look quite different … but as I said, just observe, every tree is different.
To prevent several trees from tearing at the treehouse construction during wind fluctuations, it is best to anchor it with special Treehouse Screws and Dynamic Support.