You accidentally found a good example reason for the rule to exist. It's only relatively recently (2019-2021-ish) that Germany had more pre-slided bread move than unsliced loaves.

Therefore scoping the claim being made with citations actually does improve the wiki's accuracy.

You can say bread is sold pre-sliced accurately in a colloquial sense, but actually making a claim - as an encyclopedia inherently does - should carry information on how general a claim it actually is.

Where I come from bread is normally not sold sliced. That is the exception.