I just found your post after posting a slightly different one but with possibly the same underlying reason.
Please see my post at Blueprint Bundle with Metatype deployment problem
Maybe it will give you some ideas - there is a workaround I founf which might help you too.
I have seen the same behaviour. The property name is used when the value cannot be resolved. I'm not sure what you mean when you say it works when you call your properties file. Are you importing the properties file in your blueprint? I suspect that may be what is missing.