It's a little more complicated then that. You have to have a working knowledge of the stock structure. But I guess you could use that as a rule of thumb. I just wouldn't bet my money on it, unless you are following the stock movement very close.
I would want some TA or chart reinforcing my rule of thumb guess, before trading it. Basically saying, if I noticed that happening. I'd do some in depth research on the filings & daily charting first.
Yes you got the points though.
If there is large accumulation and it doesn't go naked short fast. Someone is selling into the market, providing the shares being accumulated. (VC dumping)
If there is large blocks going thru and it does go on the SHO list fast. The M&Ms are selling naked short to help favorite large clients accumulate. (VC accumulation)
IMO from under the tinfoil hat!
News 
Market Data 
Discover 
