That's because we parameterize the query. In the first case, the query is constructed as
SELECT invoice_number FROM invoices WHERE
invoice in ($1)
where $1 is "'INV-0726', 'INV-0728', 'INV-0708'" (a string with those values chained together)
Even though the preview is the same, it's not exactly the same as the latter query.
You should be able to use ANY, with an array of string value (i.e. don't join them) like the suggestion we have in this thread:
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