Unnecesary disambiguation in Via field

Example: Journey from Tottenham Hale to Euston but setting Via to Liverpool Street.

When I enter the Via preference, I’m asked to make a selection:

image

So I choose Liverpool Street, as the icons alongside it include the relevant station options. That ought to be enough to make it clear that I want to go via the station, not by some other place.

But then JP tries to calculate the journey, and no longer understands that Liverpool Street means the station:

That doesn’t happen when I put in Liverpool Street as either source or destination, so it looks like JP is somehow handling the Via field differently to From and To.

So, why does the Via field need to be disambiguated twice?