The toolpath is not in a principle plane (i.e. G17, G18, G19 ) for portions of the cut so linear moves are expected.
Change your Motion Output Type to Arc Prep/Par to Tool and check you CLS file. You will see some CIRCLE records but not for all paths. Your post will have to bet configured to...
Same operations, just choose a bull nose end mill. See attached file.https://files.engineering.com/getfile.aspx?folder=0156f57d-2918-4968-b271-554371da6061&file=model1_john_bn.prt
I would recommend Z-Level profile for this operation. I created two sample paths, one with Z-level profile and the other with contour area.https://files.engineering.com/getfile.aspx?folder=78291d38-1ce0-43d7-9081-0fc3456d9746&file=model1_john.prt