Without background, Battery+ is useless?

So, I think I just found out that Battery+ us useless. I wanted to experiment with battery life/functionality, so after taking off the charger for this week, I've made Get Up, Stand Up my background app, and removed Battery+.

However, now, when I open Battery+, not only has it removed the estimates of when the watch will die (which I expected), but it's also deleted all past data on how long the watch has lasted.

Am I correct in assuming it's essentially useless without being the background app? I doubt it, but is there anyway to get the old data back?