It is seafood base that is the substitute. It is a substitute for real seafood stock -- easy enough to make from shrimp, lobster, and/or crab shells, aromatics, and water (plus maybe a little wine and tomato product). Any restaurant that makes fresh food does that, rather than using bases.
Depending on the caliber of the chef

it could very well be that "Better than Boullion" is what home cooks should use instead. Or Kitchen Basics Seafood Stock, which is already mixed with water. Even Knorr makes some reasonable stock cubes. However, there are powders and bases used in lesser commercial kitchens that are comparable to the horrible stuff for home cooks -- mostly salt, hydrolized yeast powder, etc., to be avoided by everyone.