We sometimes get asked if offsetting toneholes is an option.  We understand some advice does suggest that having offset toneholes can be benefical during the early stages of learning to play, but we have spent a number of years experimenting with offset toneholes and the results are in some ways surprising and at odds with the perception that offset toneholes are more ergonomic and easier to play with...
Perhaps countintuitively, offsetting toneholes does not actually bring toneholes closer together - it actually makes them further apart!
Furthermore, in terms of the ergonomics, becasue our hand position is not defined when we play a low whistle, it is actually at least as easy to find a good/comfortable position with straight alligned tone holes.   This is true irresepctive of our stage of development - beginner / intermediate / advanced.   If there was in fact any advantage then higher end whistles would adopt offset toneholes, but actually the opposite is true.
It's certainly understandable how offsetting toneholes might seem better or more sophisticated, but this is one area where keeping it simple is actually more effective.