They are probably focusing on shopify because they need to automatically ingest financial metrics for the valuation. Shopify has the transaction data so they can automatically value any company on the platform. They are probably starting with shopify since its the biggest ecommerce platfor.

Most of these target Amazon sellers, but they also roll up other independent stores. The thesis in this case that Shopify store operators are analogous to Amazon store operators, so they can use the same roll-up model on Shopify people, which isn't actually the case for many important reasons.

I'd imagine that targeting Shopify makes the process much easier for evaluation and migration.

They leave them on Shopify. Basically it is a way for owner operators to cash out if their Shopify stores have reached a certain level of revenue and the business is kinda automated.

Same thing happens with Amazon sellers.