We learn that the League of Villains have been training with Gigantomachia for over 1 month at this point. Spinner
states that they've been rotating between their members, not including Shigaraki. All of them have faced off against Gigantomachia, and we got a little peak of this.
We see Twice, Shigaraki, and Mr. Compress engaging Machia in battle.
They are shown to be injured fighting him, including Shigaraki who is
7-C. We even see
Machia launch a shockwave attack that hits all of them, showing that Mr. Compress and Twice have comparable durability to Shigaraki.
While Toga and Spinner are injury free, that's only because they weren't fighting him during this period of time.
However, early on we do indeed see they're injured from fighting Machia. They've all taken attacks from him, even his indirect attacks with shockwaves can harm them and Shigaraki.
The fact they have injuries from fighting Machia shows that they haven't just been avoiding getting damaged. No, they're taking the same attacks from Machia that can harm Shigaraki. And we know that
Machia has actually been slowing down since the beginning of this fight, so it isn't like he's massively changing his power.
So even back than he was hitting them with
7-C level of power.
We've also seen multiple members of the Liberation Army take hits from Gigantomachia, who was using even more power than when he fought Shigaraki. You can even see some Twice Doubles get sent flying by Machia as well that didn't instantly melt.
Though, they probably melted after hitting the ground or whatever.
Skeptic's puppets were also shown to take a direct hit from this Machia and not instantly fall to pieces.
They aren't scaling to Machia's level, they're scaling due to the fact the amount of power Machia is using here is strong enough to harm Shigaraki. While he was holding back during the League's fight with him, he still harmed Shigaraki and was a massive threat to him. Machia obviously scales above all of them greatly.
All of the League, Spinner, Mr. Compress, Twice, and Toga should have
7-C durability via scaling from Shigaraki due to their training with Machia. Their AP will scale accordingly if they managed to harm anyone who could physically harm them as well.
The only arguments I can think of against this scaling (At least as of this moment) can be either Machia was changing his power output depending on who he hit, which is absurd since he didn't care for anyone save Shigaraki and even he was severely injured and almost killed by Machia.
Or that they managed to avoid any actual direct hits, which is also equally absurd without any backing. We're shown they have sustained damage from fighting Machia, by this same logic we can say Shigaraki was never hit directly either. Which means even glancing indirect blows from Machia are
7-C.
Also, Shigaraki is the fastest of the group as shown during the Twice double altercation in Re-Destro's tower.
None of them were able to react to Re-Destro's attack, while
Dabi and Mr. Compress didn't even catch how he moved. So there is no way they can avoid damage from Machia better than Shigaraki can.
This line of reasoning is baseless without any evidence to support it, which doesn't exist. In fact, Mr. Compress was shown to be grabbed easily by Machia so it's pretty obvious he could land direct contact with them.