It looks like there’s a difference in the trial periods because Shopify sometimes runs different promotional offers depending on the time or region. Typically, Shopify offers a 3-day free trial, and then a 3-month trial for $1/month for certain plans (Basic, Grow, Advanced).
However, some special promotions may offer a longer 6-month trial, depending on the specific campaign, affiliate, or region you’re in.
The length of the trial period is in your local region, etc., promotions, or register route. While some entries have your typical 3-month trial, others feature an extended 6-month trial for newcomers. The store trial will follow the offer associated with the link you used. Seeing them is normal.