Yeah I entirely disagree with everyone getting up in arms about this. Do I feel sorry for OP. Definitely. Easy mistake to make first time.
But it is pretty clearly sign posted as per industry standard. And I am surprised this is coming as such a shock to ffs as over in the USA this happens all the time if you try and book J - I have had mixed fare bookings a lot, and it's not really any better sign posted here? Definitely not fair go worthy.