I think we're having a misunderstanding of the term "site" here. A core rotation site is the Hospital(s) where you will be placed for your clinical years to complete your required core clinical rotations in different specialties (Internal medicine, Family medicine, Surgery, Psychiatry, OBGYN, pediatrics, Emergency medicine).
There are 10 core sites currently for ARCOM: Fort smith-2 sites (Baptist and Mercy), Little Rock-1 site but multiple hospitals, Fayetteville/Rogers- 1 site but multiple hospitals, Searcy- 1 site (Unity health), Poplar Bluff-1 site (PB regional med. center), Pine Bluff-1 site (Jefferson regional), Hot Springs-1 site (CHI St Vincent), Durant-1 site (Alliance health), Shreveport-1 site (Willis Knighton).
You only stay in one site. if you're in Fort Smith, you'll stay there all 3rd/4th year. If you're in Little Rock, or Hot Springs, or Searcy, same thing. Now, there are elective rotations in your 4th year that you can use to schedule your own rotations in any specialty you want anywhere you want, and people usually use those for away audition rotations at different residency programs before they send their applications out for residency, or you could choose to stay at your site and complete them there as well. So no, there is no alternation between sites, unless you request to do one or more of your electives in Little Rock for example while your main site is in Fort Smith.