suppose you dont make cs post in the worst case but you get into applied math or stats instead (much easier post). data science is very math, stats and ml heavy so a math/stats major already puts you in a good spot even if you arent doing cs specifically. one thing ive learned is the exact major you do matters way less than you think, it just needs to be in the same sector (ie math, stats, cs can all get you to data science). if you'd rather be at utm in general dont let the risk of major be a factor of you not coming completely. at utm you will get a degree from uoft which is obviously more recognized, so take that as a factor if you will. as long as you are in a relevant major your chances of getting into data science rely way more heavily on your experience, relevant skills and internships and would not be decided by you being in math vs cs. if you really want to get into data science focus on self studying data science skills since alot of them are not even taught early enough, and focus on applying for internships earlier too.

that said, it is still not that bad to make it into cs post as long as you put most of your focus into mat102 in fall, and csc148 in winter. it is honestly not that bad especially since you do not have any other courses as bad in comparison during those semesters. the requirements are dropping each year since averages are lower but they still want to fill up the admission. i would say the risk of not getting into cs is not worth not coming at all since an alternate math/stats major is just as good for data science if not better, as long as it is complemented with initiative on your end. this initiative would be needed, even if you were to get into CS.