Yes, it's relevant - in fact the exact service is relevant, which is why we have integrated a feedback utility into the SeatSelector which will automatically send all of this diagnostics information. It's fine to post about it on the forum as well as using the feedback tool, we're not going to stop people discussing it, but it's frustrating not having any of the information to make it straightforward to investigate when it appears it's only been posted about here.
What stations were you booking between, on what date?
The "Send feedback" button appears only on the Seat Selection diagram, and I had no reason to use it there because the seating plan looked as I expected it to look. (In fact, because I had no issues, I probably didn't even notice the button before pressing "Confirm selection", particularly as it appears to be greyed out on my screen even though it's enabled.)
It's only on the next pop-up box, which confirms the journey and selected seat, that the discrepancy appears, and there is no feedback button on that box. I know now, by playing around, that I can go back into the seat selection diagram from that box, but it wasn't obvious, and it seems like a lot of trouble for something that was only a minor irritation.
I just did a test booking, recreated the error and sent you feedback.
With regards to improvements, I don't think I do have any actionable suggestions. I'm bewildered by the sheer number of travel options being offered to me, and by the number of ticket options available for each of them when I click through, some of which have as many as 4 or 5 splits. Sometimes I choose a service and am told that some legs of the journey have no first class available - which turns out in some cases to be half the journey or more, such as Cardiff to Manchester. I know that this is due to the complexity and sheer ridiculousness of the rail ticketing system in the UK, that you have little choice and that there is probably very little you can do about it. I'll continue to use your site for my GWR bookings (which are frequent). Thanks.