Thank you for the question, I tried a more circular low angled thumb cluster (you can see it on the top left plate) and it has its pros and cons:
As you stated the pro is the confort because our thumb movement are circular and not linear;
On the other hand the angled linear solution i found gave me the chance to fit a magnetic disc under the thumb cluster and felt more aesthetically pleasing, also because this keyboard is inspired by the little nine-nano by bsag (that has a linear thumbcluster)!
So i found that in good balance between confort, aestethic and functionality!