The underlying assumption to the question is why only one thing is allowed to be uncreated .. ? Are there others like them, much like here on Earth where we have many authors writing many books? The Bible doesn't answer those at all, it starts in media res (despite its first three words!)
(I have other complaints about such a God but)
Isaiah 44:6-8 ESV
Thus says the LORD, the King of Israel and his Redeemer, the LORD of hosts: "I am the first and I am the last; besides me there is no god. [7] Who is like me? Let him proclaim it. Let him declare and set it before me, since I appointed an ancient people. Let them declare what is to come, and what will happen. [8] Fear not, nor be afraid; have I not told you from of old and declared it? And you are my witnesses! Is there a God besides me? There is no Rock; I know not any."
contradicting science is no great flaw. "Science" contradicts itself from time to time.
What I think the parent means by contradicting science is rather different: the Bible says things which go against ideas which we believe have been verified by evidence, but the Bible won’t be changed to reflect that understanding. On the other hand, science will change its idea of what it thinks to be true as more evidence becomes available. Nobody changes things in the Bible.
Pslams 95:3 ESV
For the LORD is a great God, and a great King above all gods.
Psalms 97:7 ESV
All worshipers of images are put to shame, who make their boast in worthless idols; worship him, all you gods!
Deuteronomy 32:8 NRSV (less henotheistic in other translatins)
When the Most High apportioned the nations, when he divided humankind, he fixed the boundaries of the peoples according to the number of the gods;
And there are others. We know pretty clearly from historical sources that the early Jews were henotheistic (recognized the existence of other gods, but only worshipped YHWH), and that is preserved in the oldest parts of the Old Testament. Even Genesis often uses a plural when God talks about his works - today that is often explained as talking about himself and the angels or even the holy trinity, but it is very likely it originally referred to the god of Israel and the other (lesser) gods in the heavens.
Because how can we even apprehend anything existing outside of time?