In real and organic scenario the number of Telegram members is one of the measure of a ICO popularity.I have seen some ICOs opening second,third ,fourth telegram channels as they have reached max capacity on the main channel (max being 100k members).But now a days scammy ICOs are buying fake/paid telegram members to boost the member count.
Remember that the big guys like Bancor raised so much money and they only had 1 Telegram channel with a few hundred people but they were all ACTIVE and interested. Whereas I've seen projects like you said with 3 channels all full, but all the questions ever asked are "when listing" "when moon" and "when pump".
Organic scenario almost doesn't exist anymore for reach. When I was active on Telegram I kept getting added into channels where I realised people were just shilling their videos. So-called influencers that made me so angry for spam.