First, make sure you have subscriptions set up on your main lds.org calendar page. The default URL will only sync what you have subscribed to. I did notice an odd bug in that when I first looked at the sync, it didn't list any calendars. I went back to see what I had set up, and then all the calendars were listed in the sync.
Personally, I'd go with a custom sync. That way, only the calendars you choose will sync over. I can "view all" on lds.org, but only "sync some".
Note that it's up to Google about how often to sync. It should pull in the events immediately if the URL has changed, but won't do that if you just delete and re-add the URL. After that, the sync is about once every 24 hours.
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