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Hey Mothner As Joy mentions, the best bet for getting targeted advice here would be to share the identity of this client and the precise search you're trying to rank for. Otherwise, we can only speculate. The possibilities could range from the Possum filter to whether you've got the right categories, to a lot of other things. If you're unable to mention the client, that's perfectly okay, but it does leave the community here guessing rather than investigating.

Additional research turned up this Matt Cutts video which addresses my question head on: https://www.youtube.com/watch?v=ZjRGkc__FwQ

It's pure speculation but my guess would be that the single page would be seen as one URL and that, the page would be seen indeed as slower to load everything. But in most cases the viewport/ what's in a users view would be loaded quite fast so because of that it could be seen as 'on average'.