Hi there @ryan.aftershock0,
Thanks for posting and I believe @Bobi N. offered good info and article related to your question. Because the email needs to pull from a specific Profile, to properly test, you'll just need to send yourself a Live message (assuming you have Recently Viewed products on your test Profile). You can learn how to send a single email here: How to Email a Single Person Using Klaviyo.
Our product feeds are designed to show popular products based on the settings that are chosen, these settings will not consider any products the customer has previously viewed.
For the Viewed Product feed, Klaviyo will generate recommendations based on the products that customers have browsed in your store. Customers without existing purchase data can receive recommendations of products similar, but not identical, to the ones they have already viewed.
So the products in the block shouldn't match the profiles recently viewed products, rather it should show popular recently viewed products by all customers.
If you are looking to show the profiles recently viewed products instead, you can follow the steps here to set that up in the article shared by Bobi.
All the best,
Alex