I’ll say to his defense, that was a paltry amount of water compared to what a fire hose can shoot out so it’s understandable he wasnt impressed. The other thing to consider is up until his mom used her ice magic, he probably had only ever seen small scale magic like the laundry stuff
I’m only giving him the benefit of being impacted, I mean that.Yet consider he was around for years as a child, i.e. with the license to be inquisitive , and never thought to ask about the limits of magic nor investigate it nor read through books for records of magic? Like “If there’s fire magic, is there fire resistance magic?” or “If water can be output, how much can be output? I’ve seen a firehose in my world, is that possible in this one?” It’s that in all of that time he never seems to have even though it was possible to have powerful magic, without anything in the world dissuading him from that thought.
As I said I will give him the benefit because I attribute the lack of being impressed to simple "not being able to process the world properly" due to his trauma. An even better way for writing would be the “I searched but found 90% of people can only control X much, powerful magic doesn’t seem to be a thing here” which opens up the possibility of thematically bucking that trend or him having a boost due to being isekai’d etc.