The major yardstick used in Shopify SEO is how your Shopify store ranks for specific search terms.
That's like that standardized commodity or unit of measure that's talked about.
Like a liter. (Don't get me started on the USA and the metric system...)
"I'm ranked #1 for woman's shoes."
"I just got to spot #10 for organic dog food."
It's a good measurement of your SEO but it's only a proxy for what really matters.
You try to improve your rankings, so you can attract more search traffic because higher ranked sites are more attractive to people.
Therefore it becomes a "rank better" == "more sales" process.
But rankings aren't the only yardstick.
Just because you're ranking #1 doesn't mean that people are buying or even clicking to your store.
Sales are important.
Customers are important.
Rankings and traffic, not so much.
They are just a means to an end.
You need enough rankings and traffic to meet your sales goals but no one started a business wanting to chase down rankings in lieu of sales.
Anyways. This is where JSON-LD for SEO helps out. It won't do much or anything to improve your rankings but it can help you get Rich Snippets. Rich Snippets will let you attract more customers to your store using the existing rankings.
Think of it and Rich Snippets as a conversion optimization that you do to your SEO. Or if you will, a SEO-CRO. I'll think I'll pronounce it so-crow.
Do you need some SEOCRO?