Please attach a 2-question sample survey demonstrating the issue, Thank you.

It never work, and nobody try to work on it : hiding column can not be done easily in javascript.

It's a cosmetic issue.

I understand that it has never worked.
I noted this issue because the UI led me to believe it should work (because there were the fields).

Anyway.
Real life scenario on my table last week: I must filter by column.
Did a workaround using simply hiding nth columns based on previous answers with eg
$('#question{QID}').find('.answer td:nth-child(2),.answer th:nth-child(2)').hide();

Filtering arrays by columns is not often used but sometimes there is no way around it. I have seen commercial software do it.
I have no strong feelings about that, but I just thought maybe it was somehow intended to work (made me glad).
Would be good to have that in the long run.
If it is difficult to do now, then the fields should be hidden to avoid confusion.

for what it's worth ...
an example survey.

One more thing while discussing this type.
Not related to this issue, but what I noted while working on my columns last week.
if you set "mandatory" on this array. Its checked row by row. Sometimes it is more reasonable to make it mandatory by column (as was my case). Again - commercial software did it. I'll post a separate issue on that later :)

Yes, i know you know ;)

About actual solution : more a workaround but in plugin : https://framagit.org/SondagePro-LimeSurvey-plugin/hideEmptyColumn/blob/master/README.md

It's note the only time this issue is reported. See e.g. 13441 and I remember there were some other too.
Because I would really enjoy this feature, I'm digging in the source code to find a solution. Had some progress yet, but still a lot of steps away from a final solution.

@orvil : the issue with hiddin column against hiding line is more related to javascript :

$("tr#identity").hide() : hide line
$(col#identifty").hide() didn't hide column …