I’d say it’s normal. Somehow. There are lots of discussions around that. Anyway I wouldn’t worry. FYI I have over 120k photos in my library and whenever I change my phone or do a hrs reset it takes days even weeks to index again everything. On this beta I see it runs again a library analysis even though it was update not set up as new. And just to make things even better during this time the battery is literally killed with hours of photo background activity. But hey. I’m ok. It’s part of the process. It was my choice to use iCloud Photo Library and tbh I’m still waiting some under the hood improvements in that area.
Thanks for the reassurance. I left my phone running overnight on the charger and I'm pleased to report that all of my photos showed up in the morning. The battery was pretty warm throughout the day and a peek at the battery stats indicated that Photos (background activity) utilized 49% of my battery in the last 24 hours.