And there is nothing more to it. but I will try to elaborate:
You are right, the server should be able to handle autotraders for the next months at least. Autotraders are handled as actual online players by the emulator. Even if they don't do anything while vending, each one will have a small impact in CPU and RAM which results in added cost to the server operation and possibly lag. It is currently unknown to me what the actual limits are, bot no ressource is unlimited, so there will be issues eventually.
This might not be urgent, also correct, but during the last 10 days there where 100 vendors added to the market. In 1 year we will be at 3500 to 4000 merchants, assuming they dont get kicked by accident and the numbers of active players stays constant (although it will probably rise, hopefully 😉
The point of the suggestion is that it is already visible, that this number has a rising tendency and it affects server performance and cost. For a healthy long term operation a counter measure should be put in place.
I have asked if there are known limitations in rA Discord. I will post it here, if I get an answer.