seem pretty easy to see tbh
Yes, and that's fine if you only go there to study the page. But the average user goes there just to fill in the form, not to study the page. And that's the person we should be designing the form for, not the form coder's boss who probably never tries to use the page.
The user's line of sight is always down a column, never across the page. That's why telephone directories always go in alphabetic order down the column, never across the page.
So, the user will see first the box to fill in the activation code, and then the continue button -- but the option to activate with a voucher will never have been seen.
It's poor user interface design -- forms need to be designed for what users actually do (and the confusion in the post mentioned above is a proof of what users actually do).