It’s useful to take this as a worked example…
With OSMF’s Shortbread tiles, you can look at a different map style pointing at the same vector tiles. I used taginfo and overpass to find an example local to me, and then used this map style (one of mine) to browse to the same place. In the other map style, the oneway arrows appear, so the data is definitely in the Shortbread vector tiles.
There’s also a debug map style which tries to show “everything in every layer”**. With that you can hover over each data item and see all the attributes.
** Edit: But not “at every zoom level”, which makes it not great for debugging the “capital cities” problem mentioned elsewhere.