Hi there, @ryparken… let me start this response by saying I am not an expert by any means on Bubble performance (although I have spent a fair amount of time trying to optimize my own apps from a performance perspective), and I don’t have a definitive solution to your problem. So, in other words, feel free to stop reading right now.
The above being said, your post did remind me of this post in a thread from about a month ago…
Yes, that entire thread is about a getting a chart to load, but I remember thinking at the time that the solution could certainly apply to other situations, such as waiting for a repeating group to load.
My thinking with regard to performance has always been that there is probably only so much us Bubblers are ever going to be able to do to make things “lightening fast” in Bubble (or even if we weren’t using Bubble, for that matter). So, it’s all about the user experience when things aren’t lightening fast, and that seems to be what you are trying to address.
If you are trying to make sure the pre-loader animation stays in place until the repeating group is actually ready to be shown, the solution in that post seems like it might work well. I mean, if the animation is being shown until a condition that is the same as the repeating group’s data source is true, then it seems like you would get the desired result of showing the animation until the repeating group is actually ready to be shown.
Who knows, maybe someone with a lot more experience than I have will come along and say, “Oh, all you have to do is this!” However, any time the topic of performance comes up, there doesn’t seem to be a silver bullet, and again, your post reminded me of that post in the other thread.
Anyway, I hope this response helps in some way, shape, or form… and at the very least, it got your post back to the top of the list for a hot minute. 
Best…
Mike