It is to do with the preposition
min translated 'than' in the AV's Gen 3:1
the serpent was more subtil than any beast of the field. It comes from the same root as
miyn or 'kind'. From the idea of being part of, it takes the meaning 'from out of'. So what Gen 3:1 is saying that out of all of the beasts of the field the serpent was shrewd, or more idiomatically more shrewd than all the others.
Here is what
Gesenius says in his Hebrew Grammar
[119v] (d) מִן‎, originally (according to §101a) separation,[1] represents both the idea of distance, separation or remoteness from something, and that of motion away from something, hence also descent, origin from a place, Am 11.
[119w] (1) From the idea of separation is naturally derived on the one hand the sense of (taken) from among..., e numero, e.g. Gn 3 1 subtil as none other of the beasts, &c.; cf. 3:14, Dt 3324, 1 S 1533, Ju 524 (so especially after the idea of choosing out of[sup][2][/sup] a larger class, 1 S 228; cf. Ex 195, &c.), and on the other hand, the sense of without (separated, free from...), e.g. Is 223 מִקֶּ֫שֶׁת אֻסָּ֫דוּ‎ without the bow (i.e. without one needing to bend a bow against them) they were made prisoners; cf. Jer 4845 מִכֹּחַ‎ without strength; Ho 66, as the first half-verse shows, not more than burnt offerings (as R.V.), but and not burnt offerings; Mi 36, ψ 525, Jb 1115, 1926, 219, also such examples as Nu 1524 far from the eyes, i.e. unobserved by the congregation; Pr 203.
[sup][2][/sup] All the partitive uses of מִן‎ also come most naturally under this idea of separation out of a larger class. Thus מִן‎ is used in the sense of some, something, and even one, in such expressions as and he slew... also מִשָּׂרֵי יִשְּׂרָאֵל‎ (divers) of the princes of Israel, 2 Ch 214; מִכָּל־‎ Lv 42; 1 K 185; מִדַּם הַפָּר‎ some of the blood of the bullock, Ex 2912, &c.; Jb 276 my heart doth not reproach me מִיָּמַי‎ for any, i.e. for one, of my days; 38:12 מִיָּמֶ֫יךָ‎ one of thy days, i.e. ever in thy life (this explanation is confirmed by 1 K 16; cf. also 1 S 1445, 2528). In this way also, the frequently misunderstood Hebrew (and Arabic) idiom is to be explained, by which מִן‎ before אֶחָד‎, אַחַת‎ is equivalent to ullus; e.g. Lv 42 and shall do מֵֽאַחַת מֵהֵ֫גָּה‎ any one of these things; 5:13, Dt 157, Ez 1810; so before a nomen unitatis (see §122t), 1 S 1445 (2 S 1411, 1 K 152) מִשַּֽׂעֲרַת רֹאשׁוֹ‎ not one hair of his head.—מִן־‎ is used in the sense of the Arabic min el-beyān or explicative min (often to be simply translated by namely), e.g. in Gn 722 of all that was, i.e. so far as it was, probably also Gn 62 (=whomsoever they chose).
A being portrayed the story is a snake, left slithering on his belly eating dust. I agree with Heiser about the real significance of these curses, but he is missing the very straight forward picture presented in the story that describes a snake, even telling us the serpent was one of the beasts of the field. I agree we shouldn't try to read our scientific presuppositions into the story and that we need as best we can to understand it in terms of ANE culture. Heiser even recognises that the story is operating on two different levels, what is going on in the divine council on the mountain of God and what is happening on earth. But we need to look to how the story is told, just because we recognise a supernatural being in operation, the one Ezekiel describes as a guardian Cherub on the mountain of God, we should not read that understanding directly back into the story about the garden if it doesn't fit. We still need to take the plain meaning of the story in the garden at face value and see what it is saying, and how it is saying it. And in the story it is simply a talking snake.
I don't see it as an issue of a real Adam and Eve or not. You can still insist on real people with the story of their temptation and fall told in metaphor, as Heiser shows you can't escape metaphor in the story. But it work even more beautifully when you realise Adam and Eve are part of the metaphor too.