It sounds like it's probably a boilerplate "Thanks, but we're not interested" response, as opposed to one tailored for each applicant.
You weren't denied the opportunity to apply, as such. You were told that, based upon the qualifications you represented to them, you were rejected.Quoting crij66
That may have been a consideration, but it's not necessary to speculate -- as cbg stated, the employer is entitled to set an educational requirement for the job and reject any applicant who doesn't meet it.
Here, the gist of the question seems to be, "They said two years of college would be fine, but now they want a completed degree." The fact is, sometimes employers are so overwhelmed by applicants that they use screening requirements above the minimum job requirements in order to reduce the applicant pool to a manageable level. Increasing the educational requirement is a simple and legal way to reduce the applicant pool.
I disagree, but as I noted (consistent with what cbg said) it doesn't matter under the described scenario.

