Sadly, I think for many(most?) people 'semi formal' has gone from meaning black tie to meaning please wear a jacket with your jeans and as it is only semi formal a tie is optional.
I have no idea what terms like 'smart casual' mean. And slightly off topic, I sure don't know what 'dressy jeans' are.
I think we need some descriptive terms for dress that everyone, just not folks here, agree on so we know what level of attire is expected.