I think it's more to do with it being a scripting language. Scripting languages are designed to be quick and easy to write, so instead of having to deal with int/float etc, the language can do it for you.
Internally, float and int are completely different types, 2’s compliment vs ieee754. Conglomerating them to a “number” feels like weak typing.
(Disclaimer: I’m a grumpy C++ engineer.)
Edit: it does look like a neat/useable language though!
The problem I do see with combining int and float is that it means that you always have to be careful with == on any pair of numbers, where a language that does distinguish between the two gives you a clue about when equality will work and when it won't.
But that's a flaw in the number type, not a weakness in the type system.