Sorry, but this is incorrect.
C1 Express had a very limited feature set compared to C1 Pro. I've looked at the comparison tables several times over the years and C1 express, although good as free tool was disappointing in terms of features when compared to the full version. Some of the best reasons to buy C1 such as editing layers, color editor and sessions were not available in the express version. I have regularly, over the years, offered help to C1 users, only to discover that my advice only worked with the full version of C1, and wouldn't work with the Express version. e.g using C1 as a file browser and avoid the need for a catalogue.
Indeed, as I said, from memory ,the feature list from FRC looks very similar to the feature list of C1 express.
This page lists the advantages of the Pro version over the express version:
Create across different devices. Make instant edits with Styles & presets. Work better together with Live.
www.captureone.com
A brief comparison suggests that FRC has some features that C1 express didn't ie it supports HEIC, and Prostandard profiles