I can confirm that Shopify records the source of the FIRST click to the site and does not update it.
I can also confirm that (by default) Google Analytics records the LAST source in a session which results in a conversion (ie. Last Click).
So in some cases it will be the same (eg. the user first comes to the site from a Google organic search and decides to place an order during the same session).
But in other cases, the user may first come to the site from (say) a Google Ad, perhaps sign up for email, then return some time later via the email, or direct, or from an organic search, or whatever. In this case, Shopify will have recorded the initial source (Google Ad) and Google Analytics will have recorded the last source (or Last Click).
There are a few edge cases where GA does not capture the conversion (eg. if the users transacts on Paypal, but does not return to the site, therefore does not trigger the 'thank_you' page or the conversion tracking).
I find it useful to know BOTH:
- which traffic source initially acquires the customer, but also
- which traffic source results in a conversion
Does this make more sense James?