I just discovered here the source of my frustration and confusion over why my tests weren't passing: property scoping. I was trying to access a property defined in 'TestCase1' from 'TestCase2.' I und...
In older versions of SoapUI property expansions were limited to be within the test case or it's direct ancestors (suite, project, and global). So, they acted the way you describe wanting them to act.
However, in more recent versions, SmartBear has enhanced property expansions to be able to get data from any property in the project, whether it's in a direct ancestor or not. This is NOT an illegal reference (even though I agree with you that it generally isn't necessarily a wise reference).
If the Maven plugin had issues with your expansions, then what you hit was actually a bug in the Maven plugin, not a ReadyAPI bug.