It can, depends on the band. The "direct grounding" mostly increases gain, making the amp easier to drive, and helps increase output power on 10m/12m. It can also improve stability, since there isn't a capacitor anywhere that doesn't go through self-resonance at some frequency and above that become inductive. This is one reason why "broadband" coupling or decoupling often uses several parallel capacitors of different values. Hard to accomplish with one capacitor, especially when it has leads. Easier to accomplish with chip caps directly bonded to the required conductors, but the SB-200 doesn't provide well for that.