The above statement should be clarified a bit, as it could be misinterpreted. There are two types of Acrobat forms, both are "compatible" with Reader and Acrobat from and end user perspective. The incompatibilities mentioned are just in regards to form design.
XFA Based Forms: These are created using LiveCycle Designer (which is a windows only app). Once the .xdp file is converted to PDF users can interact with the document using Acrobat/Reader, however you will not be able to edit the form using Acrobat's form tools (to edit the form template you will need to go back to Designer). XFA based forms will still work fine on the Mac from an end user perspective (form fill, sign, submit etc...)
AcroForm: When you create forms using Acrobat, this results in an AcroForm. LiveCycle does support AcroForms for a number of operations (data extraction, assembly, flattening, archiving etc...), but if you want to route a form in Workspace and use the advanced features that XFA forms provide, then stick with XFA based forms.