It still sounds awfully similar. If you're firing ~30% of hires after the first month, then you're clearly treating it as an extended interview. And the first month of any job (in software, at least) includes a lot of training/ramp-up, so you don't expect to get much labor out of that period. The main difference is just that an internship has a several-month unpaid leave starting 3 months after hire.

I suppose it diverges more if you consider internships prior to the final one due to the weird optionality on following intern seasons, but I think that's a minority of internships due to the hiring goal (once you start looking at 2+ year lead-times before a potential full-time start date it becomes much harder to justify).