I'm not certain, but I would tend to agree with you. I found the following in Bennett's New Latin Grammar
about indefinite pronouns:
2. Aliquis (adj. aliquÄ«) is more definite than quis, and corresponds usually to the English some one, somebody, some; as,â€”
nunc aliquis dÄ«cat mihÄ«, now let somebody tell me;
utinam modo agÄtur aliquid, oh that something may be done.
4. Quisquam, any one, any one whoever (more general than quis), and its corresponding adjective Å«llus, any, occur mostly in negative and conditional sentences, in interrogative sentences implying a negative, and in clauses of comparison; as,â€”
jÅ«stitia numquam nocet cuiquam, justice never harms anybody;
sÄ« quisquam, CatÅ sapiÄ“ns fuit, if anybody was ever wise, Cato was;
potestne quisquam sine perturbÄtiÅne animÄ« Ä«rÄscÄ«, can anybody be angry without excitement?
sÄ« Å«llÅ modÅ poterit, if it can be done in any way;
taetrior hÄ«c tyrannus fuit quam quisquam superiÅrum, he was a viler tyrant than any of his predecessors.
That seems to suggest that aliquis
fits better for "some one". But again, I'm not to sure here but maybe you could post a question about the difference of the two words in the Learning Latin forum since posts there seem to get more responses.