What exactly is complicated about this? It is very simple: Different governments allow them different access. This access is often precarious and dependent on not pissing off the government in control over whichever area they operate in. This is the same problem every humanitarian organisation operating in the field has to deal with.
What is complicated here? The Iranian regime apparently cares more what they might report, presumably because the Iranian regime perceives it to be a bigger threat to their interests.
What is it you think is complicated about this? Just tell us instead of beating around the bush.
What exactly is complicated about this? It is very simple: Different governments allow them different access. This access is often precarious and dependent on not pissing off the government in control over whichever area they operate in. This is the same problem every humanitarian organisation operating in the field has to deal with.