Not necessarily. While the presence of a massive comet belt could explain the absence of Jupiter-like planets in some extrasolar systems, it is not the only possible explanation. Other factors, such as the metallicity of the protoplanetary disk or the formation and migration of giant planets, could also play a role in determining the final architecture of a planetary system. Therefore, the presence of a massive comet belt cannot be directly inferred from the absence of Jupiters. Further observations and studies are needed to understand the various factors that shape the formation and evolution of planetary systems.