Just an update on the ticket logged for the descriptions coming through to Viva Learning from SharePoint. This is the response I got from support (note: this was after about 3 weeks of communication/troubleshooting):
Hello Sarah,
As we've discussed internally about your concern and we found that the feature is not available at the moment. We really apologize for the design limitation.
You can put your ideas/suggestions in this Microsoft forum so that the Microsoft Developer team will get notified and priority on this feature.
Reference link: https://aus01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ffeedbackportal.microsoft.com%2Ffeedback%2Fidea%2Fd947eacb-d340-ec11-a81a-0022484e21f1&data=05%7C01%7CSarah.Waugh%40skyline.co.nz%7C0cfa9ed5a4e242d3bebb08da26651469%7C3f21011c062948a0b81e2207232fd7f5%7C0%7C0%7C637864512821583470%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=gD52vpI4tTmb%2BhFTSF%2Bbro424gqeGNuZkySmS8%2Ff12I%3D&reserved=0
Please feel free to ask if you have any queries.