It might help to mention what size the suit is.
It's common for sellers to under-measure so if anything the actual measurement could be wider. Impossible to know, of course.
It's a small difference and as others have said it may or may not matter. In my experience it partly depends on fabric weight and how structured it is.
You mentioned the shoulder width of your best-fitting jacket. What about your other jackets? It's good to compare to as many as possible that you...