[ghusbands]

It's not just about the validation success, but about having only one bit of code consuming the looser input and producing a definitely-correct output. If you simply validate and preserve success, you still later need to produce the output you need, and it's hard to be sure that the earlier validation and the later parsing actually agree on what is valid.

If you're talking about consuming the looser input and producing a definitely-correct output, already, then you're talking about parsing, not validation. Most validation occurs naturally during parsing.