Yes, that's true about being vaccinated over 6 months, in fact thousands of chileans lost their 'covid passport' (or whatever is called, it's only a QR code to certify you're vaccinated) because they didn't get their 3rd dose after 6 months and that's why you will be classified as non-vaccinated (if you don't take your 3rd dose before 6 months after you were fully vaccinated)

Apparently you still have some time before completing the 6 months before your second dose, so maybe You can validate your vaccines in order order to get this QR code (covid passport) and I guess things will be easier at the border, hopefully.

here you can validate your vaccines

Apparently you have to create an account with your email ( I can't tell you too much about that process since I use my chilean ID to get access). But I must tell you it's quite a pain in the ass with all the bureaucracy to validate your vaccines and get that QR code.

Well, all of the above considering you even got vaccinated in first place. If not then you will have to meet all the requirements as non-vaccinated, there is not much to do about it.