I can see how it was maybe a bit spikier in the screenshots you posted, but that's not always the case. After Trunks initially completes the process of transforming into his Super state in the same episode, his hairstyle is virtually identical to what it was before. Compare images 1 and 3:Bullza wrote:The hair was completely different though.
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[/spoiler]The anime seemed to make a much bigger deal out of his new Super form than his power after training with Vegeta, so it doesn't make any sense for Super Trunks' gains to be smaller than his gains post-training. Just comparing Super Saiyan 2 Trunks with Super Trunks in general, it would be enormously shitty writing if he'd suddenly grown significantly stronger from that one day of training if Toei never once gave us a single line of dialogue in the show to indicate that; on top of that you have his lousy performance in Episode 61 where he has to be protected by Goku and Vegeta, which itself is at complete odds with the idea that pre-Super Trunks was powerful enough to fight at a level comparable to Super Saiyan Blue just because he got a couple of shots in on Super Saiyan Rose Black. Unless it was a rage boost, it just doesn't work.
Moreover, I wouldn't say it's fair to conclude that a Kaioshin's age means that Zamasu's strength automatically grows at a much slower rate compared to some of the mortals. I don't think those two necessarily have anything to do with each other, especially since Zamasu is considered a prodigy.
