Sorry lads, retread of old turf for most of you but this nonsense keeps on persisting. If this isn't the final nail in the coffin then there is nothing more I can do. They will have to learn the hard way. Axes from Companies such as Gransfors Bruks, Hults Bruk, Ochsenkopf, Helko Werk etc are not ready to be used for heavy chopping in a stock condition. The only company that produces reasonably priced axes with decently proportioned handles is council tool, but even they can benefit from a bit of thinning. For the rest you must put time in and thin them down heavily till they are comfortable, have a good amount of flexibility and fit your hand shape best. The improvement is vast, so WHY NOT?
Forgot to add in this source, US Forest Service is also pretty clear that thick handles are bad https://www.fs.fed.us/t-d/pubs/pdfpubs/pdf18232812P/Part09_ReplacingHandles.pdf