The acceptance rate for Harvard College students applying to Harvard Medical School is approximately 6% - 8%, which is over twice the overall acceptance rate. Statistically, your best chance of acceptance to HMS is from MIT, where the acceptance rate to Harvard Medical School is closer to 10% (though the number of MIT graduates at HMS is much fewer than Harvard graduates, as so many fewer MIT students apply to medical school vs Harvard undergrads; 60 - 70 vs 250+). Other schools with considerably higher acceptance rates to Harvard Medical School include Penn and Stanford, as well as some of the top smaller liberal arts colleges such as Williams, Amherst and Swarthmore.
The answer is yes only if you look at raw numbers. Out of the ~160 matriculated students in the Pathways and HST program, roughly 40 each year come from Harvard undergrad, so on the surface it looks like you would have better odds.
Out of the 40 students, roughly 20 students are from the just-graduated class, and 20 are alumni who took some time off. You would be compared with several hundred Harvard pre-medical students who are highly ambitious, hardworking, and have impression stats and resumes. HMS could form a perfectly well-rounded, geographically diverse, class just from Harvard undergrads alone, but they don't. So going to undergrad there does not make it "easy" to get into HMS; you have to work even harder to stand out from a stellar crowd.
No matter where you attend college, it's challenging to get into a prestigious medical school. The best you can do is to be a highly competitive applicant, stand out as much as you can in your choice of extracurricular activities and awards, show the school you really want to go there, and hope for the best.