When I worked at K-Val Hobbies in Buffalo NY(now defunct) we did three runs of custom decorated SB hoppers. They were done by Third Rail Graphics. We had obtained the prototype lettering diagrams directly from Bethlehem Steel Company so the cars were perfectly reproduced in HO scale. We also did one run of gondolas using the P2K model, again, correctly done because we had the drawings from BSCO. Kadee issued SB hoppers but the lettering was the wrong color.
You’re correct that Kadee’s initial release of SB 116 (Kadee catalogue no. 7024) had incorrect white stencils. Approximately two years later and having realized the error, Kadee released their second SB model no. 7018 representing SB 7028 with the correct yellow stencils.