But the article seems to take a very roundabout way for it, and still doesn't link the direct version. I just did the same thing, googling 'UK ETA', clicked the top result, then clicked the most salient link on the result page ('Apply'), then clicked the most salient button on the next page which is a big green 'apply now button', though it is after the links to the app (but those links are not big and green). Admittedly I do have a decent amount of experience with the UK government's website which tends to have this pattern of a few pages of explanations about the thing before you get to the form you need to fill in, but it surprises me that it was that hard to find.
(Edit: ah, no, I see: the next steps are quite dark-pattern pushing you towards the app. Yeah, that's quite shitty)
No, I think he searched for the ETA App and was disappointed at the lack of emphasis on an alternative to the app once you are in it. If you just search the web for ETA and gov.uk it takes you straight to the online portal (which also asks for feedback as it's a service in Beta). The gov.uk website is neutral between you using the app or the online portal.
The only point I can see here is that once you are in the app it keeps encouraging you to use it and doesn't keep suggesting you might like to use the online portal instead. But I don't understand the initial premise about not using app stores. If the author didn't want to use an app store, why did he download an app instead of going to gov.uk?
(Edit: ah, no, I see: the next steps are quite dark-pattern pushing you towards the app. Yeah, that's quite shitty)