Can't add Google calendar to iOS with common email address (works on Mac)

I am using iCloud as my primary synchronization platform between iOS devices and my Macs.

I also have a Google account using the same email address that I use as my primary on iOS / MacOS (not a gmail account).

I can add the Google calendar associated with that email to my MacOS Calendar. However, when I try to do the same on iOS, the operation silently fails after I provide my Google login credentials to the Accounts Settings pane. (I can see the screen where I would choose which databases to sync - mail, calendar, notes, contacts - but the screen stays greyed out, then exits without giving me a chance to choose "calendar".)

I suspect that this is because the email address is already in use and configured. Given that this works Just Fine on MacOS, I'm curious whether anyone has a workaround for this?