my impression is that Shinto-ryu kenjutsu is generally only taught to exponents of Shinto Muso-ryu jo, and usually only after the exponent has been training in jo for some time. the only students in my dojo who have any training in SMR's ancillary arts are two 5-dan holders (both have just finished learning the kenjutsu kata) and the most senior of our 4-dan students (she's very close to finishing the jutte/tessen kata). i'm not certain what, if any, level of koryu license these students hold.
one japanese website states that, according to certain sources, Gonnosuke devised the jo techniques based on the techniques of what became the ancillary arts including Shinto-ryu kenjutsu. at least, this is what i'm able to gather; my ability to read japanese is not quite at a native level just yet. whether this means you might as well study the ancillary arts separately or if you should only study them as part of SMR jo training, i really can't say. if you'd like to take a look at the website in question (assuming your computer in enabled to read japanese), i can post the link later.
as to the value of learning the kenjutsu set on its own, i'm sure you'd get something out of it, but it might be more valuable as part of integral SMR training. rest assured, SMR jo training will give you plenty of practice with tachi. i'd be happy to put your questions to my teacher and see what he says. of course, you may receive a more authoritative response than mine from our moderator Dianne and others before i can get back to you. HTH.
Jeff Hamacher
Those who speak do not know,
Those who know will not speak ...
So I guess that means I don't know a thing!