It's not urban legend. Every one has their own thoughts about what each tiny even bid or ask signals. But in general you will see these makes no sense trades close usually during stalls or pre reversal/continuation.
I use to teach it's M&Ms signaling where their clients have strong orders pending or just closed by the broker. ONLY works with the OTC 2 tier system for front trading. I use to call it a vote for direction wanted. The higher the number at bid / ask the more the broker needed the price to move that way.
You usually see several of these hundred orders close over a few to 10 minutes. Then a price reversal or continuation in the direction where the most votes are cast.
Ex: the price is running strong, all of a sudden the trades stop closing for 5 / 10 minutes. (the stall) Then you see a 200 close at bid then 2 more 300 & 100. A few minutes later one at ask 500. The one at bid 100. Most brokers need to refill lower and the stall changes direction and the price falls. The concessions was down.