The symbolist has to explain the real links between a symbolist view of Gen 1 and the realist purposes to which it is put.
The symbolist view of Genesis 1, etc. would have to entail a category error of the magnitude of the undergraduate 'fallacy'.
This is the 'fallacy' committed by many under-graduates who confuse possession (e.g. of a hand out, an e-book, a website address) with knowledge (produced by having read, considered and understood the given text).
The way it pans out in theology is that on the one hand we have, we are told, a 'symbolic' representation of God's creating, for various reasons to do, it would seem, not with creating, per se, but with bragging to ANE neighbours on the 'our story is better than your story' basis.
This places the creation account on the same rhetorical level as a Goon Show script where Neddy Seagoon fronts up to battle with a picture of a gun. Nice, but useless in the real world.
The fissure between a symbol of something rendered unknown by the declaration that the only information we have about it is a 'symbol' (of something else, presumably, but without any real world correlate), and real world events and relationships that are said to depend upon, or are referred to this symbol (that's like threatening your gun totting enemy with a read from your book of Kitchener's battle of Omdurman), have got to be given a connection that crosses the category boundary of 'we are in the real world' and the symbol is not. So where is the 'real world' link to the world of symbols?
Clearly they need a consulting philosopher who is up to date with Hegel, the Greek deceivers (Plato and his pupil Aristotle: a bright pair, but they made too many ontological mistakes to get full marks), and the tail enders, the Neoplatonists.
But seriously, folks, the problem is that there can be no link. God represents himself as creator at critical places in Scripture, which references can only point back to the Genesis account (note I carefully don't say, 'accounts', mainly because I don't think that Genesis is a second temple fantasy, and I can read what the text says...clearly one event, two subject matter branches). If the account is vaguely symbolic (that is, with no identifiable reference event), then it can have no meaningful connection with any of its citations.
God uses his credential as creator inescapably as being the one who created in 6 days, as he sets out in Genesis, and therefore dependable in doing what he says he will do, of being in relationship with us, and having a fellowship with us that characterises the relationship in objective and tangible terms which make sense in the continuity of time-space-event between his actions as reported, and our experience of being in the world created, on an intellectual level, defined by those actions and God's statements in relation to those actions.
Very simply the two are in different domains of meaning with no link apart from a hollow verbal one: Creation = symbol of something unknown, God's actions = thing is real space-time contiguous with the (claimed) basic reality of God-acting-with-wisdom-in-love.