Can a conference listed as CORE 'A' have an acceptance rate of 60%?
Acceptance rate has some correlation to conference quality, but I think it's far from being the most meaningful metric, and it isn't very informative in isolation.

There can be top-tier conferences that have the same, or even higher, acceptance rate than second-tier conferences. The reason is that people know how demanding they are, so they don't even bother to submit papers that they know will be very likely rejected, while the second-tier conference might get more submissions as people have higher hopes of getting their papers accepted.

I personally think CORE is rather trustworthy (at least as far as rankings go), as in my particular subfield it's accurate. But this may depend on each subfield. If you want more evidence for the quality (or lack of) of that conference, this website aggregates three different conference rankings. And if you prefer something more quantitative, there are the Google Scholar h5-index rankings, although they should be taken with a grain of salt because this metric is very influenced by size (number of articles published per year).