Except for the 109 times in 2015 he reached via single, BB, or HBP you are absolutely correct.
i got forgot to include hbp, but without those:
salvy - 3.8% of the time clears the bases, 4.5% leaves himself in scoring position, 19.0% clogs up first in front of esky.
rios - 1.0% clears, 5.8% scoring position, 20.7% clogs up first.
so there is some tradeoff between clearing the bases in front of your worst hitter, vs having a really slow guy on first that is unlikely to score on most esky hits vs having someone very unlikely to clear the bases, leaving your worst hitter in a greater number of highly leveraged at bats.
of course, the obvious remedy is to pr gore for salvy any time him clogging up the bases is important.