Hi @Melville3ZFH5! Thanks for reaching out.
A few releases ago, we drastically improved the performance and reliability of the FormIt -> Revit pipeline. This had the unforunate side-effect of switching to Import Symbol as you mention, which limits the by-face tools in some situations.
Luckily, there is a workaround, which is listed in the FormIt + Revit help docs: You can import the FormIt model into a Mass-category family (then load it into a Revit project) to take advantage of Levels, Mass Floors, and By Face tools and apply Revit system families to FormIt geometry.
Hope this helps!
Josh Goldstein
Senior Product Manager