Just wanted to mentioned that mag07’s technique on page two of this thread works.
Setup fields in ACF
Create one record and populate each ACF field
Export posts/CPT using a plugin, I used WP Ultimate CSV Importer
Then open your CSV and copy+paste your fields from your source CSV to the appropriate column in the exported file.
Import new file using WP Ultimate CSV Importer
ACF fields will appear under “Custom Fields” and will not be restricted.
This approach is basically a more labor-intensive, but *free* alternative to simply paying for a premium plugin that will do it in one-swoop.