Talking about Ganymede, if there was highly developed extraterrestrial life on par with technology within 100 years of ours we would have detected it. Nothing about what they say excludes undeveloped extraterrestrial life or microorganisms.
Aquatic life, we have examples of intelligent aquatic life on this planet but that life does not fit the "highly developed technology" requirement. We don't know how intelligent the aquatic life is but we know it is intelligent and appears to be self-aware.
Is the development of technology a key factor in determining intelligence? That seems like a philosophical question more than a scientific question but not having the answer to that does not negate the calculations that were made which require highly developed technology of two or more civilizations simultaneously.