While it is indeed recommended to be somewhat careful about ET's making claims, in most cases, i'd say close to 100% are honest, what does that mean, undue disbelief is wrong.
As for life in this solar system, while most planets like Venus, Jupiter, Saturn etc have civilizations that evolved beyond our visual range verging on the etheric, point is many moons and some planets are inhabited on our level STARTING WITH OUR MOON.
"as early as 1950, which may be before the environments across the solar systems were well understood"
My my, this makes me cringe. You are up for a cold, cold, cold, COLD shower. As i said, starting with our Moon to everything else.