Reason for not performing full validation with reloaded parser?

[Interrante, John A (GE Research, US)]

I got curious and searched the codebase and website, but I couldn't find an 
explanation why Daffodil lets you save and reload a parser, but restricts you 
from doing one thing with a restored parser that you can do with a normal 
parser.   The only restriction Daffodil imposes is that you can't perform full 
validation with a reloaded parser.  Why is that restriction imposed?