I once fell in the same trap.

When a multires expression is used in a list of expressions without being the last element, or in a place where the syntax expects a single expression, Lua adjusts the result list of that expression to one element.

Lua 5.4 manual. 3.4.12 – Lists of expressions, multiple results, and adjustment.

So, table.unpack(…) or ... should be last in a list of expressions.

Perhaps, if you literally want to insert some values into a table, you could use table.insert()?