Hi @dennisve ,
The product reviews widget is generated via a script. Scripts load after the text and the html of the page so they will always load “after” the main components of the page have loaded. You can optimize scripts to load faster, but it would be best to contact Shopify product reviews app about this.
There are also other review apps out there the might load faster, I would personally recommend https://apps.shopify.com/judgeme. Their product review widget loads pretty fast.
Feel free to reach out!
Best,
eStoreSpeedOptimization