I'm wondering how a social worker could be on "active duty", let alone in a violent protest. I'm also wondering how a member of the emergency services on duty could be arrested.
Without details your claims do not make much sense, including your claims about precedents and likelihood of conviction.
I might be misremembering the likelihood of being convicted with "riot", but from what I can remember, several people were convicted with riot in the 2016 unrest; they were later acquitted several years later through costly appeals.
If you take part in a riot/violent protest you may be charged with a criminal offence.
This is the way it works in most countries, including the UK. There is nothing extraordinary there.
Being arrested or even charged is also not the same as being convicted.
Note that the definition also includes unlawful assembly, so the people involved would already be in the wrong.
I think some people are trying a bit too hard to excuse violent protests as if HK was somehow a special case.