The score with that tool doesn't equal speed or performance, it can be used as a guide to try to identify potential performance issues, but the score is largely based on apps used, and some quirks can make the score fluctuate wildly - one recent example: I had a site scoring 88/100. One of the warnings recommended setting a defined height and width of images on the page. This has zero affect on performance, but after implementing that the site scored 100/100.
If you want to dive a deeper into the topic this article should shed some insight for you: Understanding Load Speed + Analysis Tools and Scoring on Shopify (I wrote that with consultation from my team, Speed Boostr, that have optimized over 1,500 Shopify sites).
With any performance tool, use it as a guide but don't sacrifice engaging features or site design just to improve the score (assuming you're on an ecommerce site and your goal is to improve conversion rate).
