I suppose I can demonstrate the issue with the following two screenshots:
In my opinion, this behavior is unexpected. It should be possible to provide a (positive) boolean, as most input parameters are of this nature.
Let me know what you think. 
I can even extend on this topic further; it would be sensible to have another option for the "Type" of input, i.e. whether it's either a query, data, or boolean. I suppose the "data" option could be replaced by either "string", "number", "boolean", etc. which also helps with validation.
To illustrate: I currently parse objects as JSON (since this turns it into a string), in order to get by this limitation. I suppose that feels more like a hack.
Not meaning to dwell, but I can also envision other properties like if an input value is required or not. This is quite similar to how VueJS deals with this.
It would essentially make things more strict and there have been times where this could save you from a couple of bugs.
Hello @emozio!
I completely agree. I think the error message you shared in your first image is either
a: An issue we are currently working on fixing so that the IDE parser can consistently convert the word true to a boolean and not a string.
b: The IDE editor giving a false negative that is incorrect and should not be reflected in the component's behavior.
Could you share which component and where in the inspector you were able to find the 'Default Value' input?
Once I get more context on the modal you are looking at I can dig into making a feature request for another option to the "Type" dropdown, as to your second point.
Are you thinking that the options for "Type" would be different if it is being applied to a query vs data vs boolean?
Also on your third point, could you elaborate more? Are you saying that having another dropdown to further specify if an input should be required or not? Not super familiar with Vue (React dependent 
).