He could use Transformation Jutsu and Bunshin No Jutsu already, but like in the movie, he always failed to use them correctly and something stupid came out from them.
Also, the Kage Bunshin also failed like normal Bunshin, so even if we would avoiding the facts we can clearly say that the outcome is the same, as the clones didn't worked as they had to.
So technicaly there was no mistake, as the clones didn't work. Mentaly, some "certain fans" are riding on "he tried to use Kage Bunshin, it's a mistake, non-canon movie" while they forgot that what Naruto first used and read/learned from the scroll was Taju Kage Bunshin, a Kinjutsu, so no technical mistake.
LOL, first, I am not an "NH" as I don't even like any pairings from Naruto my dear little salty NS fangirl. ;P
Justify what?
You can't even tell why he shouldn't know about normal Kage Bunshin while what he read and learned from the scroll and managed to use first time was Taju Kage Bunshin, which is a kinjutsu unlike normal Kage Bunshin, which us used even by non-Konoha ninjas (see Kakashi Gaiden).
But for you again:
WHAT NARUTO READ AND LEARNED FROM THE SCROLL WAS TAJU KAGE BUNSHIN NO JUTSU!!
The kanjis of Taju Kage Bunshin No Jutsu:
多重影分身の術
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(kanji text)
多重 = Taju
影分身 = Kage Bunshin
の術 = No Jutsu
And what was written there: 多重影分身, and not 影分身 !
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As you can see, it's the same kanjis as "Taju Kage Bunshin No Jutsu" (多重影分身の術)!
Didn't learned a technique just by seeing it? Then how could he use:
- Sasuke's "Shishi Rendan" (Lion Combo)? By seeing him and copy it!
- Gudodama that he never had and didn't even had time to training with them after he got them? By seeing Obito and Madara using them!
So no, there are several times when Naruto used other techniques simply by seeing them and copy them. The reason why he couldn't use Kage Bunshin because he only seen it but didn't knew how to use it, while "Shishi Rendan" was a simple kicking comob, so of course he could copy it without problem.
So there was no mistake, as what Naruto read, learned and managed to use from the scroll was Taju Kage Bunshin, a kinjutsu, and what he TRIED but FAILED to use was normal Kage Bunshin.
But if you can explain why Naruto shouldn't know about normal Kage Bunshin before he read the Scroll while what he read and learned from the scroll was Taju Kage Bunshin then okay! It is the same when Sasuke used a hawk as summoning for the first time despite even Tobi didn't knew about it.
And no, it's different using a technique that every second ninja can use even outside Konoha and a technique which not only on a higher level, but also labeled as a Kinjutsu. The "Taju" kanjis weren't there for decoration.