I asked it to simplify sqrt(x)*sqrt(x) and it couldn't do it. Nor could it do really anything with sqrt. As soon as I added the following single rule, it works perfectly and does all the things you would hope it should know how to do!

const simpRules = [...(math.simplify.rules)];
simpRules.push('sqrt(n1) -> n1^0.5');
math.simplify(exp,simpRules);

I suggest adding 'sqrt(n1) -> n1^0.5' to simplify.js