Or it could be a deliberate way for the recruiter to deselecting candidates. “Oh gee, your referee didn’t reply in 48 hours (to the email we sent at late at night in Friday)”.

I would hope that recruiters - particularly in fields like teaching where there is considerable demand - would not be engaging in such reprehensible practices. I think that would also contravene some aspects of employment law (not an expert in employment law, obviously).