But is it actually used differently than brother in this context?
Understand that bro also has a pejorative connotation in some context, but that is not the case here.
If the quote was "we are operating as a fking unlicensed securities exchange in the USA brother." how is the meaning different?
I can see that they have slightly different connotations like thanks versus thank you, but that doesn't mean it it's no longer an abbreviation, which is what the parent poster was claiming
I was pointing out that "Bros" in a company name is exactly an abbreviation for "brother". It is, in effect, a different word than "bro" used in slang.
The usage of [abbreviation for brother, as in company names] is very different than the slang "bro" used to describe undesirable people, but it's not very different than the slang "bro" used in the statement quoted in this tweet -- just literal brothers versus metaphorical brothers.
I think bro is always an abbreviation for brother, but sometimes the act of abbreviating is done to save space (like company names) and sometimes to specifically impart informality/metaphor (like TFA). But that doesn't mean the unabbreviated version can't be used metaphorically as well.
Understand that bro also has a pejorative connotation in some context, but that is not the case here.
If the quote was "we are operating as a fking unlicensed securities exchange in the USA brother." how is the meaning different?
I can see that they have slightly different connotations like thanks versus thank you, but that doesn't mean it it's no longer an abbreviation, which is what the parent poster was claiming