Reply To: Primary text frame on recto only

Do you need to use the Smart Text Reflow feature? If you are just trying to import all the text when you Place it (adding additional pages), then you do not even need a text frame on the master page. I usually do not use text frames on the master page. Instead, hold down the Shift key when you click (with the place cursor). That will add additional pages.

However, because you want text only on one side of the spread, you do need to add a blank frame on the master page. Then shift click on top of that frame on the document page.

See:
https://creativepro.com/creating-two-or-more-automatic-text-flows.php