I have set up authentication of Power Pages site with Azure AD B2C, configured the site as directed and everything seems to be working apart from one significant issue. I'm wondering if anyone can spot where I've made a mistake. Here are the steps:
I have a Test User contact with a web role of Job Profile Users:

I have a Test Data Manager contact with a web role of Job Profile Managers:

Both contacts are registered with Azure AD B2C and I am able to sign into the site with their credentials:

I have assigned permissions to the Job Requirement Framework table so the Job Profile Data Managers can Read, Write, Create and Delete, but the Job Profile Users can just Read

Those permissions are displayed on a List:

If I don't sign in, I can't see any records on the list, as expected:

I then sign in as Test User:

I would hope to be only able to Read the list (as Test User), but I can Create, Edit and Delete:

Changes to data are being saved, even though I shouldn't have the permissions to Edit.

Any thoughts? Have I missed an essential step?