Interesting. I also have some Heltec V3 nodes and can easily connect with more than 100 nodes in my area. Some of them several kilometers away. There are at least 200 active nodes in my area.
If I have a Heltec node operating nearby, my Xiao node will collect numerous nodes in the list. With the Heltec node turned off I cannot see any other nodes, but if I wiggle the antenna connection on one of my Xiao nodes, I am sometimes able to collect about 30 nearby nodes.