Although this is indeed correct theoretically speaking, it has no effect whatsoever on the resulting display. Is it really worth changing?

I don't know if its truly necessary - I just wanted to post this 'issue', ignore it (close) or not is not my call :)

I would be against using %d,
unless it is really 100% sure that we will never need to pass a string to it ...

e.g. i am doing this in my views (but i am not using these Joomla language strings, instead using my own)
4 out of 7 items were deleted

notice the:
4 out of 7

so if you want to make an addition to the existing code, you will have to change the language strings back to %s,

but then you have a problem:

• think of all the translations that will have been updated to have %d

unless existing strings are causing a problem, it is best not to do this, reverting it in the future, would be problematic !

I was thinking about it, that best way would be to use %s in every single key when param is passed to a string. But again it would be a pain for translators OR not replace %d with %s in multiple files is a simple procedure, even at Crowdin.

I am setting this to needs review so a decision can be made.

Seems to me not worth the change, @yild you are correct here but at the end of the day it will change nothing but it will be work for the translation team. Thanks for bringing it up.