Prior to Dragon Ball Super, Super Saiyan 4 was Goku's strongest transformation. This form, born from love, not rage, gave ...

Full Power Super Saiyan 4 Goku is by far the strongest character ... they could be near-invincible by now, and on par with ...

then introducing a fully canonized Super Saiyan 4 transformation is a logical step. It gives Goku and Vegeta a whole new power source and understanding of Saiyan heritage to explore – plus it ...

Episode 123 ended with Goku and Vegeta releasing their full Super Saiyan Blue power. While we’ve seen Goku’s Kaioken powered version before, it was Vegeta that unveiled he too could go beyond ...

So arguably, this would place it in the same range. Thus when Goku and Vegeta train to use that instead, it would make sense to avoid a less refined version of that power seen in this form.