Except you don’t know how much space a string needs in memory. With all the other properties, the memory for each gameobject can be statically allocated in advance. Not relying on runtime heap allocations more than necessary I think is a pretty decent choice for a game engine.
And it’s not like you are blocked from passing strings to objects, you can still use messages and lookup tables.
One of the things I love the most about Defold is how minimal it is. And in my opinion, to make a small(?) engine compromise for some minor UX convenience, which is entirely on the editor side, would be an odd decision.