I just tried it and it wasn't just bad, but completely non-functioning. It returned a HTTP 500 Internal Server Error as soon as I clicked the search button:
Now this is probably solved by logging into my Emirates Skywards account first, given it was trying to send me to a single signon page:
Ok so I've logged in, then hit search, then it asked me to login again, then took my back to the starting page and I had to click search yet again (though it at least remembered my search criteria)
Now I've searched and not only hasn't it shown me any results, for trains which are definitely running, but it hasn't given me an error about no results either; it's just blank:
So now I've identified that it's uBlock Origin which needed disabling to show the results.
It's now returned me one result for getting from St Pancras to Bangor (I intentionally chose St Pancras not Euston because it doesn't have a generic London Terminals option and I wanted to see what would happen) tomorrow leaving after 12, which involves the changes at Crewe and Chester. In reality there's around 2tph between Euston and Bangor, some of which are direct:

There is no 1533 from Euston tomorrow so that ought to be fun. Interestingly, there is a 1433, so it seems the timezone conversion is fubar.
The price is then 10.4% higher than booking directly with Avanti.
Which is strange anyway because both Avanti and Emirates are selling the ticket as two singles at £178-£199 instead of the off peak return at £127.40, and potentially even cheaper with split tickets.
And of course, you can't use Railcards on the Emirates site, because that would be too helpful.
Turns out you can convince it to sell you a return ticket by selecting Euston instead of St Pancras as the origin. Which is at least an improvement on the Avanti site where you select two journeys at £89.10 each and then when you click through to the next screen it offers you the choice of a cheaper off peak return. I swear the Avanti site never used to do that and showed the 'from' price on the journey results screen first. They'll potentially lose business over that UX choice.
Emirates have an interesting quirk though when it only offers Anytime Returns instead of Off Peak Singles or Off Peak returns which are valid for the journey (making it more than double the price it should be!):
And no Advance fares showed up, which do exist for the inbound journey.
It also then has a curious 'Unavailable' label next to the 'Book' button, but it lets you book anyway. I think as this is the inbound and I'd previously selected the luxurious Anytime Return it's trying to communicate that there's no price to display. But to me that suggested it's unavailable to select/book:

I've then entered my passenger details and continued to the payment page and I get, "Checkout economics require persisted selected_offer_economics from Gateway book.":
No disabling of browser extensions or VPNs fixes the issue, so after all that I can't actually buy the tickets.
Which is probably a good thing because if you click those "Conditions apply" links you get shown the dialogue for the ticket conditions for any Anytime Return but with some curious additions:
Booking
A valid passport is required to book.
Not sure I'd be taking my passport on a train from London to Bangor!
Description
Travel is allowed via any permitted route. Break of journey is authorized, as detailed in the ticket restrictions. Anytime Return tickets are valid for outward travel from the date shown on the ticket and within 5 days from that date, and until 04:29 am after the fifth day of validity. The return portion must be used within one calendar month from the start date shown on the ticket. Children (aged 5 to 15 inclusive) are offered 50% discount. Up to two children aged under 5 may travel free of charge with each fare-paying adult. Groupsave discount for small groups between 3 and 9 adults on permitted route and train. Restrictions relatives aux bagages : trains LUMO, 1 sac à main et 1 bagage à main (dimensions maximales 63 x 41 x 27 cm). Trains AVANTI, 1 sac à main et 1 bagage à main (dimensions maximales 30 x 70 x 90 cm).
No idea why this sentence is randomly in French instead of English. I also don't know why it's giving me the dimensions for Lumo trains when I haven't selected any. Then the luggage restrictions it gives for Avanti are wrong. Avanti say you can have
three items of luggage, the largest of which cannot exceed 30x70x90cm.
[/quote]
Exchanges: Exchangeable only locally.
I'm not even sure what they mean by that. Only exchangeable in the country of travel maybe?
I've just realised it's also drip pricing. If you search for Matlock to Matlock Bath, it shows the price as £5.16, under the journey select, but then when you select it, the price in the corner changes to £6.90 (for context, two Off Peak Day Singles would be £2.80):
This is a dumpster fire.