Goku not going SSJ against Cooler now justified?

[precita]

A lot of people used to debate whether Goku was already a Super Saiyan when Cooler arrived, since the movie appears to take place in the 3 years of training for the Androids.

In the movie Goku in his base form gets all beaten up by Cooler. THEN he becomes a Super Saiyan and takes him out. Now in Super we see Goku continually fight in his weaker forms and get all beat up (against Black, also not powering up against Frost, etc), so it can be explained he did the same thing in the Cooler movie.

I always believed Goku was already a Super Saiyan in the Cooler film, and that's why he didn't make a big deal out of it when he transformed.

[SaiyanGod117]

There have actually been some theories on this topic, since Toriyama said the movies take place in alternate universe(I could be mistaken) but in this timeline Goku didn't unlocked Super Saiyan during his battle with Frezza and beat him with the Spirit Bomb instead. I accept this theory seems logical to me, it wouldn't make much sense for Goku to go Super Saiyan at the time he did.

[Captain Strawberry]

Well the movie was short so they have to end it quickly with something.

[B]

I don't know if it ever really need "justification." He didn't use Super Saiyan... until he did.

[HybridSaiyan]

It was obviously that dying bird that triggered his transformation.

[Nejishiki]

The implication seems to be that he hasn't mastered it to the point where he can freely activate it, which would be a fair assumption from the writers considering where the manga had been at (Goku vs Freeza*) during its development.

*I'm aware that the Trunks chapter had been published around this time, but it's also important to consider the production time window for the film.

[dbzfan7]

Pretty sure he didn't have full control of the form at the time. He didn't even seem to have Shunkan Ido too. It was weird.

[Adamant]

The implication seems to be that he hasn't mastered it to the point where he can freely activate it, which would be a fair assumption from the writers considering where the manga had been at (Goku vs Freeza*) during its development.

*I'm aware that the Trunks chapter had been published around this time, but it's also important to consider the production time window for the film.

Pretty much this, yeah. The movie was clearly written while Super Saiyan Goku was fighting Freeza, and just went off the assumptions that Goku killed Freeza and went back to Earth, and that Super Saiyan was not something that could get activated at will. All three assumptions were of course wrong, but they were logical enough at the time.

[Metalwario64]

I'm okay with it, because I believe I remember Goku telling Trunks that it took him a while to learn how to transform at will, though that could have been a dub line. I haven't watched that episode in a good while.

[Nejishiki]

I'm okay with it, because I believe I remember Goku telling Trunks that it took him a while to learn how to transform at will, though that could have been a dub line. I haven't watched that episode in a good while.

Trunks: "...Can I ask you a question first...?"
Trunks: "Can you become a Super Saiyan at will?"
Goku: "Yeah. I couldn't at first, but after a lot of practice I learned to control it."

[sintzu]

I think there are 3 ways to look at it :

1- Like you said he was just testing him and seeing if he could beat him without it.

2- Goku didn't transform against Freeza and this was his first time.

2- He did but he couldn't control it and he had to get really angry to do so.