You are technicaly right, but if you use logic in order to tell things that are true but do sound very different from what they actually are you are doing weaseling with weasel word.
As in "our prices are the lowest we ever did* (* on selected products)" sounds cheap but just means that you are offloading some unsaleable junk..
Or "Blue Sky initiative" sounds ecological, it just means that you called some activity "blue sky initiative"
Some ... could mean "all of them" but then it would be natural and honest to say "all of them"
Some ... could mean "the majority" but then you would be invited to use "the majority"
Actually the only legitimate reason to use "Some" is that there are no other adequate word, so it should not be "one" or "very few" nor "a significant number" or the majority or all...
Try "tragically some civilian died, but it was unavoidable due to the immediate danger M. EvilGuy posed to humanity" ...
You might want to avoid having somebody point out that you killed them all, and if you have only 1 out of 10 000 "collateral dammage" you would probably say it too..
Or to take your examples if you tell you child : Some ravens are black ... the natural answer will be ? what color are the non black ravens ... ? so unless you want to confuse him or her you will probably tell "ravens are almost always black although there are some rare exceptions" : http://img.dailymail.co.uk/i/pix/2007/06_01/ravenNNP_468x311.jpg