Ik I see. I am not a huge fan of this implicit choice.

I see. For me it makes the default case more concise while still allowing for specific field names. I don't feel very strong about it. Not sure what others think.

The old API forced you to make an explicit choice (as the field vs an explicitly named field), which I like better in this case as it avoids errors

You can make errors one way or the other. I don't think this is such a big point for the other version.

and keeps the flow of the API consistent.

True, true. Consistency is always a trump card

Btw, what's about the method rename to againstField?