The smaller networks all are pretty old, and any networks smaller than 20b predate any sort of blind spot training.
The biggest practical impact this has if you are using KataGo to analyze and review real games, is that the small nets could be very bad at certain joseki that people do sometimes play nowadays, most notably Mi Yuting’s flying dagger joseki, but also some of the sharper lines of some 3-4 point pincer josekis. Only the larger networks have ever been trained to fix the errors in judging these josekis.
Less frequently, although all KataGo nets get basic ladders correct due to having hardcoded ladder logic, the smaller nets might mess up various secondary and tertiary things - certain ladder breaker/maker tactics, as well as the rare cases where you need to play out a broken ladder (e.g. the Lee Sedol ladder) - more often than the large nets do. Even the large nets may have some trouble here, although it has been improved a bit from before due to blind spot training. Small nets might also have a bit more trouble with giant dragons.
Beyond these cases, for kyu and low-to-mid amateur dan players, I would expect smaller nets to still be fine.