I don’t quite understand why you are dismissing this person’s concerns like this. The codes are available for a very short period so there is a chance that if there is a WiFi or other network outage they genuinely could not get to the code.
It’s also not as though the UK has the best record when it comes to managing immigrants despite their promises.
You are welcome to do a quick google on what happened to Windrush immigrants, the trouble that EU immigrants have had post-brexit, and UKVI’s general rules, wait times, and fees. Much like the US, the UK’s immigration policy has been made highly hostile to many forms of immigration, limiting options for families and managing to bungle things at several junctures.
I agree that it is hard to put faith in a system like this where your immigration status relies on the availability of a network or even a single government site with no physical or offline backups.
I was not aware the share codes last that long now, the last time I used one (for work, although this was several years ago) it was only valid for 4 days and my employer refused to accept it which was a whole thing. I was under the (incorrect) impression that the system for border clearance would be worse than that. So I have changed my mind on this point despite your flippant comment, which was argumentative for no reason.
On the case of trusting the UK government to manage the immigration status digitally for people I still have my doubts. They don’t have the best track record.
I have my own UK passport now so I am a bit out of the loop but any sort of system where a person doesn’t have offline proof of their status that they can keep seems like it is open to issues (although physical only also has its issues so there are pros and cons no matter how you approach it).