Thanks @carolinan for the PR!
I tested, and this looks to work as expected.

A minor note, I noticed that now '<label for="%s" class="wp-block-search__label screen-reader-text">%s</label>', is duplicated 3 times, and the code to generate the markup is fairly similar for all 4 of the labels.

It might be worth considering storing the pattern or making a helper function for generation of the label markup.

I went ahead and approved because it works as is, and readability with the above is a matter of opinion. Figured I'd leave the note, though, so you can make a decision on whether to optimize this more.

I did that because we can't place the if statement inside the sprintf.

Definitely, however you prefer!

I do agree its not optimized, but I don't know how else to do it.
I first used a variable to hold the CSS class names, but the result was not any less code than repeating it.

I do agree its not optimized, but I don't know how else to do it.
I first used a variable to hold the CSS class names, but the result was not any less code than repeating it.

I think I found an alternative method which should simplify the code and conditions a lot... I submitted a PR against your branch in #35337 so merging that here will update this PR accordingly. Unless I missed something, I believe the logic there is the same as what we're doing here 🤔