Just bought my 4th pair of hiangles. Got my first pair at UK 9.5 then size 10 thereafter. The Adidas versions are a lot tighter, these 10's feel closer to 9.5.
Google shows similar experience: "Sheila · 3 months ago Sizing is off
My husband has been wearing the hiangle for 4 years and we have bought 4 pairs - he has always been 10.5 Just ordered a 10.5 for the first time on adidasoutdoor and the shoe is incredibly small. Not sure what happened here."
It means a slightly longer break in period for me, but be warned if you're already sizing tight.