Have never heard this view before but it is really interesting and your reasoning is excellent.
I believe few is 1/10th of humanity, a tithe. My reasoning is that Yahweh claims a tithe for Himself. Even in The New Testament this idea is carried forward. In Luke 17:11-19, ten leperous men appear before Yeshua. He sends them to show themselves to the priests and along the way, they are healed. Amazingly only one of those men, a tithe, returned to Yeshua to thank Him. I could be wrong of course, but ten is such an important number in The Bible, but we really don't know why.
Speaking on a purely a Biblical basis I can tell you 3 denotes spiritual perfection, 5 is associated with grace, 9 with judgement but 10 is a bit harder to nail down. I've really come to believe that 10 is related to that which belongs to Yahweh such as the Ten Commandments. That's just my :mho: