Yes for the most part. In the reserves you pick your rate and in the first year or so go to A school (unless you have very specific prior training and you can waive A school). When you graduate you are whatever rate you chose as a Petty Officer 3rd class (E4). Once you report back to your unit you start working on qualifications.
An example would be a Boatswain's Mate (BM) after reporting back from A school the BM3 will work on their boat crew qualification first. Then they can get qualified as a boarding team member, coxswain, boarding officer, pursuit coxswain etc.... those are qualifications. Those are currency in the Coast Guard. The more qualified you are, the more desirable you are.
I am an ME. The first qualification I got was Boarding Team Member, then boat crew, then Boarding Officer afloat (there is also BO ashore), then comms watchstander because it was winter and I was bored. There are a ton of other quals I can look at. Heck I could go for my 29' engineer qual if I wanted to or even coxswain.
Also, I highly doubt there are 0 CS positions open in the Coast Guard, there is 20k signing bonus for that rate. I know OS was listed as a critical rate and I think EM (correct me if I am wrong).
The PSU's are looking for ME's and everywhere can always use some crayon eating BM's